Magnetic position sensor system and method

ABSTRACT

A position sensor system includes a magnetic source for generating a magnetic field, and a position sensor device movable relative to the magnetic source, or vice versa. The position sensor device comprises at least three magnetic sensor elements for measuring at least three magnetic field values of the magnetic field, and a processing circuit configured for determining at least two magnetic field gradients or magnetic field differences based on the at least three magnetic field values, and for deriving from the at least two magnetic field gradients or differences a first value indicative of a position of the position sensor device, and for deriving from the at least two magnetic field gradients or differences a second value indicative of integrity of the position sensor system.

FIELD OF THE INVENTION

The present invention relates in general to the field of magnetic sensordevices and systems and methods, and more in particular to magneticposition sensor systems and devices and methods, capable of not onlydetermining a linear or angular position, but also capable of providinga signal indicative of the integrity of the system or a fault.

BACKGROUND OF THE INVENTION

Magnetic position sensor systems, in particular linear position sensorsystems and angular position sensor systems are known in the art. Theyoffer the advantage of being able to measure a linear or angularposition without making physical contact, thus avoiding problems ofmechanical wear, scratches, friction, etc.

Many variants of position sensor systems exist, addressing one or moreof the following requirements: using a simple or cheap magneticstructure, using a simple or cheap sensor device, being able to measureover a relatively large range, being able to measure with greataccuracy, requiring only simple arithmetic, being able to measure athigh speed, being highly robust against positioning errors, being highlyrobust against an external disturbance field, providing redundancy,being able to detect an error, being able to detect and correct anerror, having a good signal-to-noise ratio (SNR), etc.

The present invention is mainly concerned with position sensor systemsfor use in harsh environments, such as e.g. for automotive, industrialand robotic applications, where the primary function of the sensorsystem is to determine a linear or angular position, even in thepresence of electromagnetic disturbance signals, and where faultdetection is an important support function to guarantee functionalsafety.

SUMMARY OF THE INVENTION

It is an object of embodiments of the present invention to provide amagnetic position sensor system comprising a magnetic source and asensor device, and which is capable of providing position informationand fault information (or integrity information) in a manner which isinsensitive to an external disturbance field.

It is a particular object of embodiments of the present invention toprovide a magnetic position sensor system capable of detecting a faultcondition, e.g. related to the mechanical mounting of the magneticsource.

It is an object of particular embodiments of the present invention toprovide such a system comprising a magnetic source, where the sensordevice is capable of detecting the presence or absence of the magneticsource.

It is an object of particular embodiments of the present invention toprovide an angular position sensor system comprising a permanent magnetwhich is rotatable about a rotation axis, and where the sensor devicepreferably has a measurement range of 360° or 180°.

It is an object of particular embodiments of the present invention toprovide a linear position sensor system comprising an elongated magneticstructure.

It is an object of embodiments of the present invention to provide sucha system, where the determination of a fault or the system integrityrequires less processing power or only simple arithmetic.

These and other objectives are accomplished by a system, a device, and amethod provided by the present invention.

According to a first aspect, the present invention provides a positionsensor system, comprising: a magnetic field source for generating amagnetic field; a position sensor device movable relative to themagnetic field source or vice versa, the position sensor devicecomprising: at least three magnetic sensitive elements for measuring atleast three magnetic field values of said magnetic field; a processingcircuit configured for obtaining said at least three magnetic fieldvalues, and for determining at least two magnetic field gradients or atleast two magnetic field differences based on said at least threemagnetic field values, and for deriving from said at least two magneticfield gradients or from said at least two magnetic field differences afirst signal (or a first value) indicative of a position (e.g. linear orangular position) of the magnetic source relative to the position sensordevice (or vice versa); wherein the processing circuit is furtherconfigured for deriving from said at least two magnetic field gradientsor from said at least two magnetic field differences a second signalindicative of a fault (e.g. an electrical fault and/or a mechanicalfault) or the integrity of the position sensor system.

The fault signal (or integrity signal) may e.g. be indicative of thepresence or absence of the magnetic source.

It is a major advantage of determining the relative position based onmagnetic field gradients or magnetic field differences, because suchposition is highly insensitive to an external disturbance field.

It is a major advantage of this system that it not only provides a firstsignal (or first value) indicative of the position (e.g. linear orangular), but also provides a second signal indicative of a fault,because in this way certain problems (e.g. electrical defects and/ormechanical defects, such as a defective Hall element, or a brokenmagnet) can be detected, and the overall system in which this positionsensor system is used, can be made safer.

As far as is known to the inventors, magnetic field gradients ormagnetic field differences are not used in the prior art forfault-detection or for verifying electrical or mechanical or systemintegrity.

It is a major advantage that the integrity signal itself is also basedon magnetic field gradients or magnetic field differences, such that theintegrity signal itself is also highly insensitive to an externaldisturbance field.

This system is ideally suited for use in a harsh environment, such ase.g. an automotive environment, an industrial environment, or a roboticenvironment.

In an embodiment, in each sensor position only a single magnetic fieldcomponent (e.g. Bz oriented perpendicular to the semiconductorsubstrate) is measured (see for example FIG. 1 to FIG. 4 and FIG. 14(a)to FIG. 16(d)).

In an embodiment, two orthogonal magnetic field components (e.g. Bx andBz, or Bx and By) are measured in each of two different sensor locations(see for example FIG. 5 to FIG. 11 ), e.g. a first and a second sensorlocation, which sensor locations are preferably spaced apart by at atleast 1.0 mm, e.g. by about 1.5 to about 2.5 mm, e.g. by a distance ofabout 2.0 mm.

The sensor device may be further configured for providing said firstsignal or value as a position signal, and for providing said secondsignal or value (or a value derived therefrom) as an integrity signaland/or a warning signal and/or an error signal.

In an embodiment, the position sensor device is further configured foroutputting the first signal indicative of the relative position, and foroutputting the second signal or a signal derived therefrom as a separatesignal.

In an embodiment, the first signal is provided (e.g. as a digital signalor as an analog signal) on a first output port, and the second signal isprovided (e.g. as a digital signal or as an analog signal) on a secondoutput port different from the first output port.

In an embodiment, the first signal and the second signal are provided asseparate values in a serial bit-stream.

In an embodiment, the sensor device is movable with respect to themagnetic source.

In an embodiment, the magnetic source is movable with respect to thesensor device. For example, the magnetic source may be mounted to arotatable axis, and the sensor device may be mounted to a stator or to aframe.

In an embodiment, the sensor device comprises at least three magneticsensor elements oriented in a single direction; and the processingcircuit is configured for determining at least three magnetic fielddifferences based on said at least three magnetic field values, and forderiving said first signal from said at least three magnetic fielddifferences; and for deriving said second signal from said at leastthree magnetic field differences.

In an embodiment, the sensor device is further configured fordetermining said second signal as a polynomial expression of said atleast two magnetic field gradients, the polynomial expression having anorder of at least two.

In an embodiment, the sensor device is further configured fordetermining said second signal as a polynomial expression of said atleast two or said at least three magnetic field differences, thepolynomial expression having an order of at least two, e.g. as a sum ofsquares of said differences.

The coefficients may be predetermined during design, or may bedetermined during a calibration test and written in a non-volatilememory (e.g. flash) embedded in the sensor device), and may be read fromsaid non-volatile memory during actual use of the device.

In an embodiment, the polynomial expression is a second order polynomialwith non-zero first-order terms, e.g. according to the formula: secondsignal=A*sqr(gradient1)+B*sqr(gradient2)+C*(gradient1*gradient2)+D*(gradient1)+E*(gradient2)+F,wherein gradient1 is a first gradient derived from said at least threemagnetic field values, and gradient2 is a second gradient derived fromsaid at least three magnetic field values, different from the firstgradient, and A, B, C, D, E and F are constant values, e.g.predetermined values. Each of the value A and B is different from zero.The values C, D, E and F may be equal to zero, or may be different fromzero.

In a particular embodiment, the values of C and D and E are equal tozero.

In a particular embodiment, the values of C and D and E and F are equalto zero.

In an embodiment, the polynomial expression is a third order polynomialor a fourth order polynomial.

In an embodiment, coefficients of the polynomial expression are chosensuch that the second signal is substantially constant (within apredefined tolerance margin of ±25%, or ±20%, or ±15%, or ±10%, or ±5%),irrespective of the relative position, for envisioned (valid) positionsin a correct mechanical mounted system.

In an embodiment, the sensor device is further configured fordetermining said second signal as a sum of absolute values of said atleast two or said at least three magnetic field gradients.

In an embodiment, the sensor device is further configured fordetermining said second signal as a sum of absolute values of said atleast two or said at least three differences.

In an embodiment, the second signal is chosen such that the secondsignal is substantially independent of the relative position, over theentire measurement range.

With “substantially constant” is meant within a relatively small rangearound a predefined value, e.g. within a range of ±25% around saidpredefined value, or within a range of ±20% around said predefinedvalue, or within a range of ±15% around said predefined value, or withina range of ±10% around said predefined value, or within a range of ±5%around said predefined value, or even within a range of ±2% around saidpredefined value.

It is an advantage of this embodiment that the second signal issubstantially constant for any position of the sensor device withrespect to the magnetic source, because it allows to check (inter alia)the integrity of the mechanical mounting, e.g. to detect a mechanicalmounting problem, without knowing or without taking into account theactual position.

In an embodiment, the sensor device is further configured for comparingthe second signal with at least one threshold value, and for providingan output signal (e.g. a warning signal and/or an error signal)corresponding to an outcome of the at least one comparison.

In an embodiment, the position sensor system is connected to an externalprocessor, and is configured for providing the second signal (or a valuederived therefrom) to said external processor, and the externalprocessor is configured for comparing the second signal with at leastone threshold value.

In this embodiment, the actual comparison is performed outside of thesensor device, e.g. in an external processor, e.g. in an ECU.

In an embodiment, the position sensor system is connected to an externalprocessor, and is configured for providing the at least two gradientvalues or the at least two gradient signals or the at least two or theat least three magnetic field differences to said external processor,and the external processor is configured for calculating the secondsignal based on these at least two gradients or these at least two or atleast three differences.

In this embodiment, the actual calculation of the second signal isperformed outside of the sensor device, e.g. in an external processor,e.g. in an ECU.

In an embodiment, the position sensor device is configured foroutputting the first signal indicative of the relative position and isfurther configured for comparing the second signal with a firstthreshold value (T1) and with a second threshold value (T2), and forproviding a second output signal indicative of whether the second signalis a value between the first and the second threshold value.

In an embodiment (e.g. as illustrated in FIG. 1 to FIG. 4 or FIG. 14(a)to FIG. 16(d)), the magnetic field source is a permanent magnet (e.g. aring magnet or a disk magnet), rotatable about a rotation axis; and thesensor device is configured for determining an angular position, and islocated substantially on said axis. Such mechanical arrangement is alsoreferred to herein as an “on-axis” arrangement.

In an embodiment, the magnetic field source is a permanent magnet havingat least four poles, (e.g. an axially magnetized four-pole or six-poleor eight-pole disk magnet, or an axially magnetized four-pole orsix-pole or eight-pole ring magnet), and the sensor device comprises asemiconductor substrate oriented substantially orthogonal to therotation axis, the semiconductor substrate comprising a plurality of atleast four pairs of sensor elements, each pair configured for measuringmagnetic field values (e.g. Bx, By, Bu, By) in different directions(e.g. X, Y, U, V) parallel to the substrate; and the sensor device isfurther configured for determining at least four magnetic fieldgradients or magnetic field differences associated with said at leastfour pairs of signals.

The second signal may be a polynomial expression of two different linearcombinations of said at least four magnetic field gradients ordifferences, or a value derived therefrom.

The second signal may be a weighted sum of squares of two differentlinear combinations of said at least four magnetic field gradients ordifferences, or a value derived therefrom.

In an embodiment, the at least eight sensor elements are located on avirtual circle.

In an embodiment, the magnetic field source is a permanent magnet havingfour poles, (e.g. an axially magnetized four-pole disk magnet, or anaxially magnetized four-pole ring magnet), and the semiconductorsubstrate comprises at least eight sensor elements located on a virtualcircle; and the sensor device is configured for determining at leastfour magnetic field gradients (e.g. dBx/dy, dBy/dx, dBu/dv, dBv/du)along at least four different directions (e.g. U,V,X,Y) parallel to thesubstrate and angularly spaced by 45°; and the second signal iscalculated in accordance with the following formula:

Signal2=(dBx/dx−dBy/dy)², or according to the following formula:

Signal2=(dBu/du−dBv/dv)²+(dBx/dx−dBy/dy)², or a value derived therefrom.

In an embodiment (e.g. as illustrated in FIG. 4(c)), the magnetic fieldsource is a two-pole permanent magnet, (e.g. a bar magnet or adiametrically magnetized two-pole disk magnet, or a diametricallymagnetized two-pole ring magnet, or an axially magnetized two-pole diskmagnet, or an axially magnetized two-pole ring magnet), and the sensordevice comprises: a semiconductor substrate oriented substantiallyorthogonal to the rotation axis, the semiconductor substrate comprisingat least three or at least four sensor elements, each sensor elementconfigured for measuring a magnetic field component (e.g. Bz) orientedin a direction substantially perpendicular to the semiconductorsubstrate; and the sensor device is further configured for determiningtwo magnetic field gradients (e.g. dBz/dx; dBz/dy) of said magneticfield values (e.g. Bz) along two orthogonal directions (e.g. X, Y)parallel to the semiconductor substrate.

The second signal may be determined as a weighted sum of squares ofthese gradients.

In an embodiment (e.g. as illustrated in FIG. 4(b)), the semiconductorsubstrate contains four horizontal Hall elements without IMC (IntegratedMagnetic Concentrators), located on a virtual circle, angularly spacedapart by 90°.

In an embodiment (e.g. as illustrated in FIG. 4(c)), the semiconductorsubstrate contains three or only three horizontal Hall elements withoutIMC (integrated magnetic concentrators), two of these being located on avirtual circle, spaced apart 90°, one of these being located in thecentre of the virtual circle, thus forming an L-shape or a right-angledtriangle.

In an embodiment, the second signal is the sum or weighted sum ofsquares of these magnetic field gradients, or a value derived therefrom.The sum can e.g. be written in mathematical form as:signal2=(dBz/dx)²+(dBz/dy)². The weighted sum can e.g. be written as:signal2=A·(dBz/dx)²+B·(dBz/dy)².

The sensor device may furthermore test whether this sum lies in apredefined range, or may for example calculate a square-root of thissum, and test whether the square root is smaller than a first thresholdvalue or larger than a second threshold value, etc.

In an embodiment (see e.g. FIG. 5 to FIG. 10 ), the magnetic fieldsource is a permanent magnet, rotatable about a rotation axis; and thesensor device is configured for determining an angular position, and islocated at a non-zero distance from said rotation axis. For example, thesensor device may be located such that its magnetic centre is located ata distance of at least 3 mm, or at least 4 mm from said rotation axis.

In an embodiment (see e.g. FIG. 5 ), the magnetic field source is atwo-pole permanent magnet, (e.g. a diametrically magnetized two-poledisk magnet, or a diametrically magnetized two-pole ring magnet, or anaxially magnetized two-pole disk magnet, or an axially magnetizedtwo-pole ring magnet) and the sensor device is configured for measuringfirst magnetic field components (e.g. Bx) oriented in a circumferentialdirection (e.g. X) about the rotation axis, and second magnetic fieldcomponents (e.g. By) oriented in a radial direction (e.g. Y) withrespect to the rotation axis; and the sensor device is configured fordetermining a first magnetic field gradient (e.g. dBx/dx) of the firstmagnetic field components (e.g. Bx) along said circumferential direction(e.g. X), and for determining a second magnetic field gradient (e.g.dBy/dx) of the second magnetic field component (e.g. By) along saidcircumferential direction (e.g. X); and the sensor device is furtherconfigured for calculating the second signal as a function of this firstand second magnetic field gradient, for example as the sum of thesquares of these magnetic field gradients.

In an embodiment (e.g. as illustrated in FIG. 5 and FIG. 8 ), thepermanent magnet is a ring magnet having an inner radius (Ri) and anouter radius (Ro), and the sensor device is located such that itsmagnetic centre is located at a distance (Rs) between said inner radiusand said outer radius, e.g. substantially halfway between said inner andouter radius.

In an embodiment (e.g. as illustrated in FIG. 6 or FIG. 7 ), themagnetic field source is a two-pole permanent magnet, (e.g. adiametrically magnetized two-pole disk magnet, or a diametricallymagnetized two-pole ring magnet, or an axially magnetized two-pole diskmagnet, or an axially magnetized two-pole ring magnet) and the sensordevice is configured for measuring first magnetic field components (e.g.Bx) oriented in a circumferential direction (e.g. X) about the rotationaxis, and second magnetic field components (e.g. Bz) oriented in adirection (e.g. Z) parallel to the rotation axis; and wherein the sensordevice is configured for determining a first magnetic field gradient(e.g. dBx/dx) of the first magnetic field components (e.g. Bx) alongsaid circumferential direction (e.g. X), and for determining a secondmagnetic field gradient (e.g. dBz/dx) of the second magnetic fieldcomponents (e.g. Bz) along said circumferential direction (e.g. X); andthe sensor device is further configured for calculating the secondsignal as a function of this first and second magnetic field gradient,for example as a sum or weighted sum of the squares of these magneticfield gradients.

In an embodiment, the permanent magnet has an outer radius (Ro), and thesensor device is located such that its magnetic centre is located at adistance (Rs) in the range from 80% to 120% of said outer radius, or inthe range from 90% to 110% of said outer radius, or in the range from95% to 105% of said outer radius.

In an embodiment (e.g. as illustrated in FIG. 8 ), the magnetic fieldsource is a permanent magnet having at least four poles, (e.g. anaxially magnetized four-pole or six-pole or eight-pole disk magnet, oran axially magnetized four-pole or six-pole or eight-pole ring magnet)and the sensor device is configured for measuring first magnetic fieldcomponents (e.g. Bx) oriented in a circumferential direction (e.g. X)with respect to the rotation axis, and second magnetic field components(e.g. Bz) oriented in a direction (e.g. Z) parallel to the rotationaxis; and the sensor device is configured for determining a firstmagnetic field gradient (e.g. dBx/dx) of the first magnetic fieldcomponents (e.g. Bx) along said circumferential direction (e.g. X), andfor determining a second magnetic field gradient (e.g. dBz/dx) of thesecond magnetic field components (e.g. Bz) along said circumferentialdirection (e.g. X); and the sensor device is further configured forcalculating the second signal as a function of this first and secondmagnetic field gradient, for example as the sum or weighted sum of thesquares of these magnetic field gradients.

In an embodiment (e.g. as illustrated in FIG. 9 and FIG. 10 ), themagnetic field source is a permanent magnet having at least four poles,(e.g. an axially magnetized four-pole or six-pole or eight-pole diskmagnet, or an axially magnetized four-pole or six-pole or eight-polering magnet) and the sensor device is configured for measuring firstmagnetic field components (e.g. Bx) oriented in a circumferentialdirection (e.g. X) with respect to the rotation axis, and secondmagnetic field components (e.g. Br) oriented in a radial direction withrespect to the permanent magnet; and the sensor device is configured fordetermining a first magnetic field gradient (e.g. dBx/dx) of the firstmagnetic field components (e.g. Bx) along said circumferential direction(e.g. X), and for determining a second magnetic field gradient (e.g.dBr/dx) of the second magnetic field components (e.g. Br) along saidcircumferential direction (e.g. X); and the sensor device is furtherconfigured for calculating the second signal as a function of this firstand second magnetic field gradient, for example as the sum or weightedsum of the squares of these magnetic field gradients.

In an embodiment, the permanent magnet has an outer radius (Ro), and thesensor device is located such that its magnetic centre is located at adistance (Rs) of 105% to 200% of said outer radius, or in the range from105% to 150% of said outer radius, or in the range from 105% to 140% ofsaid outer radius. Furthermore, in this embodiment, the sensor device ispreferably located at an axial position substantially halfway between abottom surface and a top surface of the permanent magnet.

In an embodiment (e.g. as illustrated in FIG. 11 ) the magnetic fieldsource is a magnetic structure having an elongated shape extending in afirst direction (e.g. X) and having a plurality of at least two, or atleast three, or at least four magnetic poles magnetized in a seconddirection (e.g. Z) substantially perpendicular to the first direction(e.g. X); and the sensor device is movable in the first direction (e.g.X) relative to the magnetic structure, or vice versa, and is configuredfor determining a linear position in the first direction (e.g. X); and adistance (measured in the second direction, e.g. Z) between the sensordevice and the magnetic structure is substantially constant; and thesensor device is configured for measuring first magnetic fieldcomponents (e.g. Bx) oriented in the first direction (e.g. X), andsecond magnetic field components (e.g. Bz) oriented in the seconddirection (e.g. Z); and the sensor device is configured for determininga first magnetic field gradient (e.g. dBx/dx) of the first magneticfield component (e.g. Bx) along said first direction (e.g. X), and fordetermining a second magnetic field gradient (e.g. dBz/dx) of the secondmagnetic field component (e.g. Bz) along said first direction e.g. (X);and the sensor device is configured for calculating the second signal asa function of this first and second magnetic field gradient, for exampleas the sum or weighted sum of the squares of these magnetic fieldgradients.

Preferably the magnetic structure has a symmetry plane parallel to thefirst direction (e.g. X) and second direction (e.g. Z), and preferablythe sensor device is located such that its magnetic center is locatedsubstantially in this symmetry plane.

According to another aspect, the present invention is also directed to asensor device for use in any of the above-mentioned position sensorsystems, e.g. for use in an automotive or industrial or roboticenvironment.

According to another aspect, the present invention also provides amethod of determining a position and of determining a fault or anintegrity of a sensor system according to the first aspect. The methodcomprises the steps of: a) measuring at least three magnetic fieldvalues of said magnetic field; b) determining at least two magneticfield gradients or at least two or at least three magnetic fielddifferences based on said at least three magnetic field values; c)deriving from said at least two magnetic field gradients or from said atleast two or said at least three magnetic field differences a firstsignal indicative of a position of the sensor device; d) deriving fromsaid at least two magnetic field gradients or from said at least two orsaid at least three magnetic field differences a second signalindicative of a fault, or indicative of an integrity of the positionsensor system, e.g. indicative of the presence or absence of themagnetic source in the vicinity of the sensor device.

This method is ideally suited for use in a harsh environment, such ase.g. an automotive environment, an industrial environment, or a roboticenvironment.

The method may further comprise the step of providing said first signalas a first output signal and providing said second signal as a secondoutput signal. The first and second output signal may be analog signalsor may be digital signals, or one signal can be digital, and the othersignal can be analog.

In an embodiment, step d) comprises: determining said second signal as apolynomial expression of said at least two magnetic field gradients,e.g. as a sum or weighted sum of squares of gradient signals, or as asum of squares of difference signals, or as a sum of absolute values ofdifference signals.

The method may further comprise the step of: obtaining coefficients ofsaid polynomial expression from a non-volatile memory.

The method may further comprise step e) of: comparing the second signalwith at least one threshold value or with at least two threshold values;and outputting at least one signal (e.g. a warning signal and/or anerror signal) corresponding to an outcome of said at least onecomparison or said at least two comparisons.

Particular and preferred aspects of the invention are set out in theaccompanying independent and dependent claims. Features from thedependent claims may be combined with features of the independent claimsand with features of other dependent claims as appropriate and notmerely as explicitly set out in the claims. These and other aspects ofthe invention will be apparent from and elucidated with reference to theembodiment(s) described hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1(a) shows an angular position sensor system according to anembodiment of the present invention. This position sensor systemcomprises a four pole magnet rotatable around a rotation axis, and asensor device located in an “on-axis” position and having eighthorizontal Hall elements and an IMC structure.

FIG. 1(b) shows a plot showing the magnitude of a difference between twogradients, in the example |dBx/dx−dBy/dy| for various locations in thevicinity of the rotation axis.

FIG. 2 shows an angular position sensor system according to anotherembodiment of the present invention. This position sensor systemcomprises a four-pole magnet rotatable around a rotation axis, and asensor device located in an “on-axis” position and having four verticalHall elements configured for measuring radial magnetic field components.

FIG. 3 shows an angular position sensor system according to anotherembodiment of the present invention. This position sensor systemcomprises a four-pole magnet rotatable around a rotation axis, and asensor device located in an “on-axis” position and having four verticalHall elements configured for measuring circumferential magnetic fieldcomponents (i.e. field components oriented tangential to an imaginarycircle having a center located on the rotation axis).

FIG. 4(a) and FIG. 4(b) show an angular position sensor system accordingto another embodiment of the present invention. This position sensorsystem comprises a two-pole magnet rotatable around a rotation axis, anda sensor device located in an “on-axis” position and having fourhorizontal Hall elements without IMC (Integrated Magnetic Concentrator).

FIG. 4(c) shows an angular position sensor system according to anotherembodiment of the present invention, where the sensor device 415 hasthree horizontal Hall elements, two of which are located on a virtualcircle, and one of which is located in the center of the virtual circle.

FIG. 4(d) shows simulation results of a sum of squares of differencesbetween each of the Hall elements on the circle and the central element,as may be used in embodiments of the present invention forfault-detection.

FIG. 4(e) shows simulation results of a sum of absolute values ofdifferences between each of the Hall elements on the circle and thecentral element, as may be used in embodiments of the present inventionfor fault-detection.

FIG. 5 , including FIGS. 5(a) to 5(e), shows an angular position sensorsystem according to another embodiment of the present invention. Thisposition sensor system comprises a two-pole magnet rotatable around arotation axis, and a sensor device located in an “off-axis” position(e.g. above or below the magnet), and configured for measuring twocircumferential field components and two radial field components. Thesensor device has a substrate oriented substantially perpendicular tothe rotation axis.

FIG. 6 , including FIGS. 6(a) to 6(f), shows an angular position sensorsystem according to another embodiment of the present invention. Thisposition sensor system comprises a two-pole magnet rotatable around arotation axis, and a sensor device located near a “corner” position andconfigured for measuring two circumferential and two axial fieldcomponents. The sensor device has a substrate oriented substantiallyperpendicular to the rotation axis.

FIG. 7 , including FIGS. 7(a) to 7(e), shows an angular position sensorsystem according to another embodiment of the present invention. Thisposition sensor system comprises a magnet (e.g. a two-pole or four-polemagnet, or a magnet having more than four-poles) rotatable around arotation axis, and a sensor device located near a “corner” position, andconfigured for measuring two circumferential and two axial fieldcomponents. The sensor device has a substrate oriented substantiallyparallel to the rotation axis.

FIG. 8 , including FIGS. 8(a) and 8(d), shows an angular position sensorsystem according to another embodiment of the present invention. Thisposition sensor system comprises a four-pole magnet rotatable around arotation axis, and a sensor device located in an “off-axis” position(e.g. above or below the magnet), and configured for measuring twocircumferential and two axial magnetic field components. The sensordevice has a substrate oriented substantially perpendicular to therotation axis.

FIG. 9 , including FIGS. 9(a) to 9(d), shows an angular position sensorsystem according to another embodiment of the present invention. Thisposition sensor system comprises a four-pole magnet rotatable around arotation axis, and a sensor device located in a plane substantiallyperpendicular to the rotation axis and located substantially midwaybetween the top and bottom of the magnet. The sensor device isconfigured for measuring two circumferential and two radial magneticfield components.

FIG. 10 , including FIGS. 10(a) to 10(e), shows an angular positionsensor system according to another embodiment of the present invention.This position sensor system comprises a four-pole magnet rotatablearound a rotation axis, and a sensor device having a substrate orientedsubstantially parallel to the rotation axis and located substantiallymidway between the top and bottom surface of the magnet. The sensordevice is configured for measuring two circumferential and two radialmagnetic field components.

FIG. 11 , including FIGS. 11(a) to 11(c), shows a linear position sensorsystem according to another embodiment of the present invention. Thisposition sensor system comprises a multi-pole magnetic structure havingan elongated shape extending in a first direction and having a pluralityof magnetic poles magnetised in a second direction substantiallyperpendicular to the first direction, and a sensor device configured formeasuring two magnetic field components oriented in the first directionand two magnetic field components oriented in the second direction.

FIG. 12 illustrates a flowchart of a method of determining a firstsignal indicative of a position, and a second signal indicative of afault or of the integrity of a position sensor system, wherein both thefirst and the second signal are insensitive to an external disturbancefield.

FIG. 13 is a schematic block diagram of an exemplary position sensordevice according to an embodiment of the present invention.

FIG. 14(a) and FIG. 14(b) show another sensor system according to anembodiment of the present invention, comprising a two-pole magnet and asensor device comprising three horizontal Hall elements located on avirtual circle and angularly spaced apart by multiples of 120°;

FIG. 14(c) shows simulation results of a sum of squares of differencesbetween pairs of two magnetic field components; FIG. 14(d) showssimulation results of a sum of absolute values of differences betweenpairs of two magnetic field components.

FIG. 15(a) and FIG. 15(b) show another sensor system comprising atwo-pole magnet and a sensor device comprising three horizontal Hallelements located on a virtual circle and angularly spaced apart bymultiples of 120°, and a fourth horizontal Hall element located in thecenter of the circle; FIG. 15(c) shows simulation results of a sum ofsquares of differences between each of the Hall elements on the circleand the central element; FIG. 15(d) shows simulation results of a sum ofabsolute values of differences between each of the Hall elements on thecircle and the central element.

FIG. 16(a) and FIG. 16(b) show another sensor system comprising atwo-pole magnet and a sensor device comprising three horizontal Hallelements located on a virtual circle and angularly spaced apart bymultiples of 120°; FIG. 16(c) shows simulation results of a sum ofsquares of differences between each magnetic field component and anaverage of the three signals; FIG. 16(d) shows simulation results of asum of absolute values of differences between each magnetic fieldcomponent and an average of the three signals.

The drawings are only schematic and are non-limiting. In the drawings,the size of some of the elements may be exaggerated and not drawn onscale for illustrative purposes. Any reference signs in the claims shallnot be construed as limiting the scope. In the different drawings, thesame reference signs refer to the same or analogous elements.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The present invention will be described with respect to particularembodiments and with reference to certain drawings, but the invention isnot limited thereto but only by the claims. The drawings described areonly schematic and are non-limiting. In the drawings, the size of someof the elements may be exaggerated and not drawn on scale forillustrative purposes. The dimensions and the relative dimensions do notcorrespond to actual reductions to practice of the invention.

Furthermore, the terms first, second and the like in the description andin the claims, are used for distinguishing between similar elements andnot necessarily for describing a sequence, either temporally, spatially,in ranking or in any other manner. It is to be understood that the termsso used are interchangeable under appropriate circumstances and that theembodiments of the invention described herein are capable of operationin other sequences than described or illustrated herein.

Moreover, the terms top, under and the like in the description and theclaims are used for descriptive purposes and not necessarily fordescribing relative positions. It is to be understood that the terms soused are interchangeable under appropriate circumstances and that theembodiments of the invention described herein are capable of operationin other orientations than described or illustrated herein.

It is to be noticed that the term “comprising”, used in the claims,should not be interpreted as being restricted to the means listedthereafter; it does not exclude other elements or steps. It is thus tobe interpreted as specifying the presence of the stated features,integers, steps or components as referred to, but does not preclude thepresence or addition of one or more other features, integers, steps orcomponents, or groups thereof. Thus, the scope of the expression “adevice comprising means A and B” should not be limited to devicesconsisting only of components A and B. It means that with respect to thepresent invention, the only relevant components of the device are A andB.

Reference throughout this specification to “one embodiment” or “anembodiment” means that a particular feature, structure or characteristicdescribed in connection with the embodiment is included in at least oneembodiment of the present invention. Thus, appearances of the phrases“in one embodiment” or “in an embodiment” in various places throughoutthis specification are not necessarily all referring to the sameembodiment but may. Furthermore, the particular features, structures orcharacteristics may be combined in any suitable manner, as would beapparent to one of ordinary skill in the art from this disclosure, inone or more embodiments.

Similarly, it should be appreciated that in the description of exemplaryembodiments of the invention, various features of the invention aresometimes grouped together in a single embodiment, figure, ordescription thereof for the purpose of streamlining the disclosure andaiding in the understanding of one or more of the various inventiveaspects. This method of disclosure, however, is not to be interpreted asreflecting an intention that the claimed invention requires morefeatures than are expressly recited in each claim. Rather, as thefollowing claims reflect, inventive aspects lie in less than allfeatures of a single foregoing disclosed embodiment. Thus, the claimsfollowing the detailed description are hereby expressly incorporatedinto this detailed description, with each claim standing on its own as aseparate embodiment of this invention.

Furthermore, while some embodiments described herein include some butnot other features included in other embodiments, combinations offeatures of different embodiments are meant to be within the scope ofthe invention, and form different embodiments, as would be understood bythose in the art. For example, in the following claims, any of theclaimed embodiments can be used in any combination.

In the description provided herein, numerous specific details are setforth. However, it is understood that embodiments of the invention maybe practiced without these specific details. In other instances,well-known methods, structures and techniques have not been shown indetail in order not to obscure an understanding of this description.

In this document, the term “magnetic sensor device” or “sensor device”or “position sensor device” refers to a device comprising a substrate,preferably a semiconductor substrate, comprising at least two “magneticsensor elements”. The sensor device may be comprised in a package, alsocalled “chip”, although that is not absolutely required.

In the embodiments shown in FIG. 5 to FIG. 10 , (where the sensor deviceis not located with its magnetic center on the rotation axis), theBx-component typically refers to the magnetic field component orientedin a direction parallel to the movement direction in case of a linearposition sensor, or tangential to the movement trajectory in case of acurved trajectory, and the By-component refers to the magnetic fieldcomponent parallel to the semiconductor plane, perpendicular to theBx-component. The Bx and By components are also referred to herein as“in-plane magnetic field components”, because they are oriented parallelto the semiconductor plane of the sensor device. In these embodiments,the Bz component typically refers to the magnetic field componentoriented perpendicular to the sensor substrate. The Bz component is alsoreferred to herein as “out-of-plane component”.

In this document, the expression “spatial derivative” or “derivative” or“spatial gradient” or “gradient” are used as synonyms. In the context ofthe present invention, the gradient is typically determined as adifference between two values obtained from magnetic sensors which aresensitive in the same direction, and which are spaced apart from eachother, or as the sum of two values if the sensor elements from whichthey are obtained are sensitive in opposite directions. Thus, thederivative dBx/dx is typically calculated herein as (Bx1−Bx2), where Bx1means the Bx component measured at a first location, and Bx2 means theBx component measured at a second location spaced apart from the firstlocation by a distance “dx” along the X-axis, but the mathematicaldivision by “dx” is typically omitted. Likewise, dBy/dx is typicallycalculated as (By1−By2), where By1 means the By component measured at afirst location, and By2 means the By component measured at a secondlocation spaced apart from the first location by a distance “dx” alongthe X-axis, but the mathematical division by “dx” is typically omitted.However, for example in FIG. 2 and FIG. 3 , the gradient dBx/dx iscalculated as the sum of Vh0 and Vh1 (not the difference), because thevertical Hall elements H0 and H1 are oriented in opposite directions.

In this document, the expression “first value” and “first signal” can beused interchangeably. Likewise, the expression “second value” and“second signal” can be used interchangeably.

In this document, the term arctan function or atan 2 function refer toan arctangent function. The reader not familiar with the atan 2 function(or “2-argument arctangent” function) may for example refer tohttps://en.wikipedia.org/wiki/Atan2 for more information. In the contextof the present invention, the formulas arctan(x/y), atan 2(x,y),arccot(y/x) are considered to be equivalent.

In this document, the term “circumferential direction with respect tothe rotation axis” and “circumferential direction with respect to themagnet” and “direction tangential to a virtual circle having a centerlocated on the rotation axis” are used interchangeably. In theembodiments of FIG. 5 to FIG. 10 , this direction is denoted by theX-axis (as seen by the sensor device).

The present invention relates to position sensor system in harshenvironments, such as automotive, industrial and robotic applications.One challenge in such environments is to achieve accurate resultsdespite potentially relatively large disturbance signals. Anotherchallenge is related to functional safety. The design of safety-relatedapplications may be governed by safety standards such as ISO26262 andIEC61508.

More specifically, the present invention proposes a magnetic positionsensor system capable not only of providing an accurate position signal,but also capable of providing a second signal indicative of theintegrity of the system, or stated in other words, capable of indicatinga fault condition, e.g. an electrical and/or mechanical fault condition.One such fault condition is the loss of the magnet, e.g. due tomechanical forces exerted upon the magnetic source, for example whenmounted on a shaft.

In order to solve this problem, the present invention proposes aposition sensor system comprising a magnetic field source (e.g. apermanent magnet or a permanent magnet structure) and a position sensordevice. The magnetic field source is configured for generating amagnetic field. The position sensor device is movable relative to themagnetic field source, or vice versa. The position sensor devicecomprises at least three magnetic sensitive elements for measuring atleast three magnetic field values of said magnetic field; and aprocessing circuit configured for determining at least two magneticfield gradients or at least two or at least three magnetic fielddifferences based on said at least three magnetic field values, and forderiving from said at least two magnetic field gradients or from said atleast two or at least three magnetic field differences a first signalindicative of a position of the magnetic source relative to the positionsensor device (or vice versa), and for deriving from said at least twomagnetic field gradients or from said at least two or at least threemagnetic field differences also a second signal indicative of a faultcondition or of the integrity, e.g. mechanical integrity or a mechanicalfault condition of the position sensor system, e.g. indicative of thepresence or absence of the magnetic source, or indicative of amechanically misaligned magnet or a physically broken magnet.

Magnetic position systems where spatial gradients are used to determinea linear or angular position are known in the art, but as far as isknown to the inventors, such systems have no provisions for detecting(e.g. mechanical) fault conditions, for example either no provision atall, or no provision which is robust against an external disturbancefield. The inventors of the present invention however surprisingly foundthat the gradient signals can also be used to determine mechanicalmounting problems, such as the loss of the magnetic source.

The second signal indicative of a fault (e.g. system fault) or of theintegrity (e.g. mechanical integrity or system integrity) may bedetermined as a polynomial expression of said at least two magneticfield gradients or differences, for example as a second order functionof these gradients or differences. It is an advantage that nogoniometric function is required to calculate such second signal.

In particular embodiments, the second signal is calculated as a sum orweighted sum of the squares of the two gradient or difference signals.In other embodiments (e.g. FIG. 1 ), the second signal is calculated asa sum of the square of a first difference between two gradient signals,and the square of a second difference between two gradient signals.

Although not absolutely required, preferably the second signal issubstantially independent of the actual position, or in other words, issubstantially constant over the envisioned measurement range. Thisoffers (inter alia) the advantage that the (e.g. mechanical) integritycan be assessed without actually calculating the position, and thus canbe evaluated at a different frequency than the determination of thecurrent position.

Optionally, the position sensor device is further adapted for comparingthe second signal with one or more predefined threshold values (e.g.hardcoded in a micro-controller or stored in a non-volatile memoryduring production or during a calibration test), for example in order totest whether the second signal lies in a predefined range or not. Thesensor device may be further configured for providing an output signaldepending on the outcome of the at least one comparison, for exampleindicative of a “good condition” (e.g. when the signal has a valueinside the predefined range between the threshold values), or an “errorcondition” (e.g. when the signal has a value outside of said predefinedrange, e.g. is larger than the upper threshold or is smaller than thelower threshold).

As will become clear further, the underlying principles of the presentinvention are applicable for various mechanical configurations, forexample:

for angular position sensor systems (see e.g. FIG. 1-10 ) as well aslinear position sensor systems (see e.g. FIG. 11 );for various magnetic sources (e.g. a two-pole disk magnet or a two-polering magnet, or a four-pole disk magnet or a four-pole ring magnet, or aring or disk magnet with more than four poles);for different topologies, e.g. for angular position sensor systems wherethe sensor device is mounted at various locations with respect to themagnetic source, for example in a so called “on-axis” position (see e.g.FIG. 1-4 ), or in a so called “off-axis position” (see e.g. FIG. 5 andFIG. 8 ), or “in the corner” (see e.g. FIG. 6 and FIG. 7 ), or “outsidethe magnet” also referred to herein as “near the equator” (see e.g.FIGS. 9 and 10 );for sensor devices having a substrate mounted in various orientations(e.g. parallel to the rotation axis, or perpendicular to the rotationaxis);for sensor device having various kinds of sensor elements, for exampleonly horizontal Hall elements with IMC (e.g. FIG. 1 a , FIG. 5 c , FIG.6 e , FIG. 7 d , FIG. 8 c , FIG. 8 d , FIG. 9 c , FIG. 10 d , FIG. 11 b, FIG. 11 c ), only horizontal Hall elements without IMC (e.g. FIG. 4 b, FIG. 4 c , FIG. 14(a), FIG. 15(a), FIG. 16(a)), both horizontal Hallelements and vertical Hall elements (e.g. FIG. 6 f , FIG. 8 e , FIG. 10e , FIG. 11 d ), only vertical Hall elements (e.g. FIG. 2 , FIG. 3 ,FIG. 5 d , FIG. 5 e , FIG. 7 e , FIG. 9 d ), but other sensor elementsmay also be used, for example magneto-resistive elements (not shown).

Referring now to the Figures.

FIG. 1(a) shows an angular position sensor system 100. This positionsensor system comprises a four pole ring magnet 102 or a four-pole diskmagnet rotatable around a rotation axis, and a sensor device 101 locatedin a so called “on-axis” position (or more accurately stated: having amagnetic center which is located substantially on the rotation axis ofthe magnet), and having eight horizontal Hall elements H0 to H7 and anIMC structure (referred to herein as a “sun-structure”) having a centraldisk surrounded by eight radially oriented IMC elements having asubstantially trapezoidal shape. The sensor device has a semiconductorsubstrate which is oriented substantially perpendicular to the rotationaxis. Such a sensor arrangement, albeit with twelve Hall elements and a“sun structure” with twelve IMC elements is known from WO2014029885A1(FIG. 27 ), but the sensor device described in WO'885 only provides aposition signal, not an integrity signal or a fault signal.

Referring back to FIG. 1(a) of the present invention, it can beunderstood that a first signal indicative of the angular position θ ofthe magnet 102 relative to the sensor device 101 (or vice versa) can bedetermined, for example in accordance with the following formula:

signal1=arctan[(Vh1−Vh3+Vh5−Vh7)/(Vh0−Vh2+Vh4−Vh6)]  [1a]

where Vh0, Vh1, Vh2, etc. is the signal (e.g. voltage) obtained fromHall element H0, H1, H2, etc. This signal is highly insensitive to anexternal disturbance field in any direction. The mechanical position θmay then be derived from the first signal as follows:

signal1=2*θ  [1b]

The second signal indicative of a fault or of the integrity of thisposition system can for example be calculated in according in accordancewith the following formula:

signal2=(Vh1−Vh3+Vh5−Vh7)²+(Vh0−Vh2+Vh4−Vh6)²  [1c]

If the mechanical mounting is all right, this signal is substantiallyconstant, and independent of the angular position. This value can forexample be predetermined during design or can for example be measuredduring a calibration test and stored in a volatile memory. In case of amechanical mounting problem, for example if the magnet would no longerbe present (e.g. because it was inadvertently removed due tovibrations), the measured value for signal2 would no longer be equal tothe above mentioned constant value. Thus, by measuring this value, afault of the position sensor system can be detected, or statedotherwise, the integrity of the position sensor system can bedetermined.

It is noted that (Vh1+Vh5) can be considered a gradient signal (orspatial derivative) of a magnetic field component Bu oriented in theU-direction along the U-axis, and can thus be written as dBu/du.Typically a gradient is calculated as a difference (not a sum) betweentwo parallel vectors pointing in the same direction, but in FIG. 1(a)the gradient is calculated as a sum because the sensitivity of the Hallplates H1 and H5 and associated IMC elements are opposite along theU-axis.

Likewise (Vh3+Vh7) is a gradient signal, which can also be written asdBv/dv,

-   -   and (Vh0+Vh4) is a gradient signal, which can also be written as        dBx/dx,    -   and (Vh2+Vh6) is a gradient signal, which can also be written as        dBy/dy.

Thus, the second signal can also be written as:

Signal2=(dBu/du−dBv/dv)²+(dBx/dx−dBy/dy)²  [1d]

where each of the X, Y, U and V axis are parallel to the semiconductorsubstrate of the sensor device, and where the U-axis, Y-axis and V-axisare located at 45°, 90° and 135° respectively with respect to theX-axis, measured in anti-clockwise direction.

As can be appreciated, in formula [1a] and [1d] each of the terms of thefirst square and the second square has a coefficient of +1 or −1, but inpractice coefficients different from +1 or −1 may also be used, forexample in order to take into account sensitivity mismatch of the sensorelements and/or gain mismatch of the amplifiers (not shown). Suitable oroptimal coefficients may be determined for example during a calibrationtest, and stored in a non-volatile memory 1321 of the sensor device (seee.g. FIG. 13 ).

FIG. 1(b) shows a plot showing the magnitude of a difference between thetwo gradients dBx/dx and dBy/dy, for various locations in the vicinityof the rotation axis. As can be appreciated from the drawing, thismagnitude is substantially constant within the imaginary circle, in theexample of FIG. 1B having a radius of about 2 mm.

The second signal may also be determined as:

Signal2=(dBu/du)²+(dBx/dx)²  [1e]

where the X and U axis define an angle of 45°.

In variants of the position sensor system shown in FIG. 1 , a six-poleor eight-pole magnet is used, or a magnet with more than eight poles. Inthis case, the sensor structure would have to be adjusted such that thenumber of sensor elements is twice the number of poles.

In FIG. 12 a flow-chart of a method 1200 which is performed by sensordevices of the present invention, such as e.g. sensor device 101 of FIG.1 will be shown, and in FIG. 13 a block-diagram of such a sensor devicewill be shown.

FIG. 2 shows an angular position sensor system 200 according to anotherembodiment of the present invention. This position sensor system 200comprises a four-pole magnet 202, e.g. a radially magnetized or axiallymagnetized four-pole ring magnet or four-pole disk magnet) rotatablearound a rotation axis, and a sensor device 201 located in an “on-axis”position (meaning: having a magnetic centre located substantially on therotation axis). The sensor device 201 preferably comprises asemiconductor substrate and is preferably oriented such that thesubstrate is substantially orthogonal to the rotation axis. The sensordevice has four vertical Hall elements H0 to H3 located on a virtualcircle, each configured for measuring a radial magnetic field componentof the magnet field generated by the magnet 202. In the example of FIG.2 the vertical Hall elements are oriented such that their axes ofmaximum sensitivity are directed radially outward (as schematicallyindicated by the arrow), but the invention will also work if thevertical Hall elements are oriented with their axes of maximumsensitivity radially inwards, or even with some oriented radiallyinwards, and others radially outwards, if the values are properly addedor subtracted.

In the particular example shown in FIG. 2 , the angular position of themagnet can be calculated for example based on the following formula:

signal1=arctan[(Vh0+Vh1)/(Vh2+Vh3)]  [2a]

The mechanical position θ may be derived from the first signal asfollows: signal1=2*θ. The first signal is insensitive to an externaldisturbance field. According to the present invention, a second signalis determined which is indicative of a fault or of the integrity of thesensor system, e.g. electrical integrity and/or mechanical integrity.This signal may e.g. be calculated in accordance with the followingformula:

signal2=(Vh0+Vh1)²+(Vh2+Vh3)²  [2b]

This can also be written as:

signal2=(dBx/dx)²+(dBu/du)²  [2c]

where the X and U axis define an angle of 45°.

In a variant (not shown) of the embodiment shown in FIG. 2 , the sensordevice 201 has more than four vertical Hall elements, for example eightvertical Hall elements, located on the imaginary circle, orientedradially inwards or outwards, and spaced apart by 45°. In this case, thesecond signal may be calculated as the sum of two terms, each term beingthe square of a linear combination of four signals, for example a firstorder polynomial where each of the coefficients is +1 or −1 depending onthe orientation of the vertical Hall elements (inwardly or outwardly).As described above, one or more of the coefficients may be differentfrom +1 or −1.

FIG. 3 shows an angular position sensor system 300 according to anotherembodiment of the present invention. This position sensor system 300comprises a four-pole magnet 302, e.g. a radially or axially magnetizedfour-pole ring magnet or four-pole disk magnet) rotatable around arotation axis, and a sensor device 301 located in an “on-axis” position(meaning: having a magnetic centre located substantially on the rotationaxis). The sensor device 301 preferably comprises a semiconductorsubstrate and is preferably oriented such that the substrate issubstantially orthogonal to the rotation axis. The sensor device hasfour vertical Hall elements H0 to H3 located on a virtual circle, andconfigured for measuring circumferential magnetic field components (i.e.tangential to the virtual circle) of the magnetic field generated by themagnet 302. In the example of FIG. 3 the vertical Hall elements H0 to H3are oriented such that their axes of maximum sensitivity all point inclockwise direction, but the invention will also work if the verticalHall elements are oriented with their axes of maximum sensitivitypointing in anti-clockwise direction, or even with some oriented inclockwise direction, and others in counter-clockwise direction, if thevalues are properly added or subtracted.

In the particular example shown in FIG. 3 , the angular position of themagnet can be calculated for example based on the following formula:

signal1=arctan[(Vh0+Vh1)/(Vh2+Vh3)]  [3a]

The mechanical position θ may be derived from the first signal asfollows: signal1=2*θ. The first signal is insensitive to an externaldisturbance field. According to the present invention, a second signalis determined which is indicative of a fault or of the integrity of thesystem, e.g. electrical integrity and/or mechanical integrity. Thissignal may e.g. be calculated in accordance with the following formula:

signal2=(Vh0+Vh1)²+(Vh2+Vh3)²  [3b]

This can also be written as:

signal2=(dBy/dx)²+(dBv/du)²  [3b]

where the X, Y, U and V-axis are parallel to the substrate, and wherethe U-axis, Y-axis and V-axis define an angle of 45°, 90° and 135°respectively with respect to the X-axis in counter-clockwise direction.

In a variant (not shown) of the embodiment shown in FIG. 3 , the sensordevice has more than four vertical Hall elements, for example eightvertical Hall elements, located on the imaginary circle, oriented suchthat their axes of maximum sensitivity are tangential to the imaginarycircle, and pointing in clockwise or anti-clockwise direction, andspaced apart by 45°. Also in this case, the second signal may becalculated as the sum of two terms, each term being the square of alinear combination of four signals, for example a first order polynomialwhere each of the coefficients is +1 or −1 depending on the orientationof the vertical Hall elements (inwardly or outwardly).

FIG. 4(a) and FIG. 4(b) shows an angular position sensor system 400according to another embodiment of the present invention. This positionsensor system 400 comprises a two-pole magnet, e.g. a bar magnet, or adiametrically or axially magnetized disk magnet or ring magnet,rotatable around a rotation axis, and a sensor device 401 located in an“on-axis” position and having only three, or only four horizontal Hallelements without IMC (Integrated Magnetic Concentrator). The sensordevice 401 preferably comprises a semiconductor substrate, and ispreferably oriented such that the substrate is substantially orthogonalto the rotation axis, hence the horizontal Hall elements are configuredfor measuring magnetic field components Bz oriented substantiallyparallel to the rotation axis.

In the embodiment of FIG. 4(b), the sensor device 401 has fourhorizontal Hall elements H1 to H4, located on a circle, and angularlyspaced apart by 90°.

The first signal indicative of angular position may be calculated as:

signal1=arctan[((Vh0−Vh2)/(Vh1−Vh3)]  [4a]

The mechanical position θ may be derived from the first signal asfollows: signal1=θ. The first signal is insensitive to an externaldisturbance field. According to the present invention, a second signalis determined indicative of a fault or of the integrity of the system,e.g. electrical and/or mechanical integrity of the system. This signalmay e.g. be calculated in accordance with the following formula:

signal2=(Vh0−Vh2)²+(Vh1−Vh3)²  [4b]

This can also be written as:

signal2=(dBz/dx)²+(dBz/dy)²  [4c]

where the X and Y axis are parallel to the substrate, and define anangle of 90°, and where the Z-axis is perpendicular to the substrate.

In the embodiment of FIG. 4(c), the sensor device 451 has only threehorizontal Hall elements, namely one horizontal Hall element Hc locatedin the centre of a virtual circle, and two horizontal Hall elements H0,H1 located on the circle, and angularly spaced apart by 90°. In thisembodiment, a first signal indicative for the mechanical position, maybe calculated in accordance with the following formula:

signal1=arctan[(Vh0−Vhc)/(Vh1−Vhc)]  [4d]

and the second signal, indicative of a fault or the integrity of thesystem (e.g. electrical and/or mechanical integrity), may be calculatedas:

signal2=(Vh0−Vhc)²+(Vh1−Vhc)²  [4e]

This can also be written as:

signal2=(dBz/dx)²+(dBz/dy)²  [4f]

where the X and Y axis are parallel to the substrate, and define anangle of 90°, and where the Z-axis is perpendicular to the substrate.

FIG. 4(d) shows simulation results of a sum of squares of differencesbetween each of the Hall elements H0, H1 on the circle on the one hand,and the central element Hc on the other hand, e.g. in accordance withthe formula:

Signal2=(Vh1−Vhc)²+(Vh0−Vhc)²

wherein Signal2 is the signal indicative of a fault or system integrity,and Vh0, Vh1 are the signals obtained from the two horizontal Hallelements H0, H1 located on the virtual circle, and Vhc is the signalobtained from the horizontal Hall element Hc located in the center.

Since the horizontal Hall elements H0, H1, Hc are oriented in the same(Z) direction, each of the difference signals (Vh1−Vhc) and (Vh0−Vhc) issubstantially insensitive to an external disturbance field, and hencealso the sum of the squares of these difference signals is highlyinsensitive to an external disturbance field.

In the example shown, the sum is constant over the full 360° measurementrange. In practice, there may be a small variation on the signal. Bycalculating the sum and by comparing the sum with a first thresholdsmaller than said constant, and/or by comparing the sum with a secondthreshold larger than said constant, and by testing whether the sum is avalue lower than the first threshold, and/or larger than the secondthreshold and/or a value between these two thresholds, it is possible todetect certain faults. In a practical implementation, an average valueor median value may be determined during design and may be hardcoded, oran average value or median value may be determined during a calibrationtest and stored in a non-volatile memory 1321 of the sensor device 1320,which may be retrieved during actual use.

The first threshold may be a value in the range from 75% to 99% of theabove-mentioned average value, e.g. equal to about 75%, or equal toabout 80%, or equal to about 85%, or equal to about 90%, or equal toabout 95%, or equal to about 96%, or equal to about 97%, or equal toabout 98%. The second threshold may be a value in the range from 101% to125% of the above-mentioned average value, e.g. equal to about 102%, orequal to about 103%, or equal to about 104%, or equal to about 105%, orequal to about 110%, or equal to about 115%, or equal to about 120%, orequal to about 125%.

As a numerical example, if the individual signals have an amplitude of1.0, the difference signals would also have an amplitude of about 1.0,and the average value of the sum of squares would be equal to about 1.0.If the first threshold would be set at 85% of 1.0 (approximately 0.85),and the second threshold would be set at 115% of 1.0 (approximately1.15), the second signal will indicate that the “system integrity is OK”if the calculated signal is a value in the range from 0.85 to 1.15 andwill indicate that “a fault has occurred” if the calculated sum is avalue outside this range.

FIG. 4(e) shows simulation results of another second signal Signal2′indicative of a fault, which is a variant of the formula of FIG. 4(d),wherein the second signal Signal2′ is calculated as a sum of absolutevalues of differences between pairs of two magnetic field components,e.g. in accordance with the formula:

Signal2′=abs(Vh1−Vhc)²+abs(Vh0−Vhc)²

where signal2′ is the signal indicative of a fault or of the systemintegrity, Vh1, Vh0 are signals provided by the horizontal Hall elementslocated on the virtual circle, Vhc is the signal provided by thehorizontal Hall element located in the center, or derived therefrom,e.g. after amplification, digitization, etc. Since all horizontal Hallelements are oriented in the same direction (Z, perpendicular to theplane of the semiconductor substrate), each of the difference signals(Vh1−Vhc) and (Vh0−Vhc) is substantially insensitive to an externaldisturbance field, and hence also the sum of the absolute values ofthese differences is highly insensitive to an external disturbancefield.

As a numerical example, if the original signals Vh1, Vh0 have anamplitude of 1.0, the difference signals will have an amplitude of about1.0, and the sum of the absolute values of these differences will bevalues in the range from about 1.00 to about 1.41. Thus, the averagevalue is equal to about 1.20, and “valid” sums of absolute values ofdifferences are values in the range from about 1.00 to about 1.41, whichis about 1.20+/− about 18%.

In practice, taking into account typical tolerances (e.g. mechanicalmounting tolerances), a slightly larger tolerance margin may be chosen,for example ±20%, or ±22%, or ±24%, or ±26%, or ±28%, or ±30%. Ofcourse, the larger this tolerance range, the less sensitive the faultdetection.

When comparing the examples of FIG. 4(d) and FIG. 4(e), it shall beclear that the sum of squares of FIG. 4(d) allows to choose a muchsmaller tolerance than the sum of absolute values of FIG. 4(e), but theformula of FIG. 4(d) requires the calculation of a square (thus amultiplication), which is more demanding that the calculation of anabsolute value. Depending on the processor capabilities (e.g. hardwaremultiplier yes/no), the skilled person can choose the second signal ofFIG. 4(d) or that of FIG. 4(e).

FIG. 5 shows an angular position sensor system 500 according to anotherembodiment of the present invention. This position sensor system 500comprises a two-pole magnet (e.g. a diametrically magnetized ring ordisk magnet) 502 rotatable around a rotation axis, and a sensor device501 located in an “off-axis” position, (e.g. “under the ring” or “underthe disk”) and configured for measuring two circumferential fieldcomponents (Bx) and two radial magnetic field components (By) as seen bythe magnet.

The sensor device 501 preferably comprises a semiconductor substrate andis preferably oriented such that the substrate is substantiallyorthogonal to the rotation axis. In the embodiments shown in FIG. 5 ,the substrate of the sensor device is located at a predefined distance“g” (e.g. from 0.5 to 5.0 mm, e.g. equal to about 2.0 mm) from a bottomor top surface of the ring or disk magnet. The magnetic center of thesensor device is located at a distance “Rs” from the rotation axis (e.g.at least 1.4 mm, or at least 1.6 mm, or at least 1.8 mm, or at least 2.0mm, or at least 2.5 mm, or at least 3.0 mm from the rotation axis). Inthe example of FIG. 5 , the magnet 502 is a ring magnet with an innerradius Ri and an outer radius Ro, and Rs is preferably a value betweenthe inner radius Ri and the outer radius Ro.

If an orthogonal coordinate system XYZ is connected to the sensordevice, such that the X-axis is tangential to a circumferentialdirection, and the Z-axis is parallel to the rotation axis, and theY-axis is oriented radially (i.e. perpendicular to the rotation axis)then the first signal, indicative of the angular position of the magnetrelative to the sensor device, or vice versa, may be calculated asfollows:

signal1=arctan[K·(dBx/dx)/(dBy/dx)]  [5a]

where K is a constant, which may be chosen such that the amplitude ofK*(dBx/dx) is substantially equal to the amplitude of (dBy/dx).

FIG. 5(c) to FIG. 5(d) show various sensor structures which may be usedto calculate these gradients. The sensor device of FIG. 5(c) uses a socalled “dual disk” structure comprising horizontal Hall elements andIMC. More information about this structure can be found in US2018372475,incorporated herein by reference in its entirety. Such disks may forexample have a diameter of about 150 to about 250 micron, hence thedistance between two corresponding Hall elements may be in the order ofabout 200 micron. The distance between the centres of the two disks maybe in the order of 1.5 mm to 2.5 mm, e.g. equal to about 2.0 mm. Thesensor device of FIG. 5(d) comprises two pairs of vertical Hallelements, spaced apart by a distance “dx” along the X-axis. Using thelatter sensor structure, the value of dBx/dx can be calculated as(H2−H4), and the value of dBy/dx can be calculated as (H1−H3). But othersensor structures may also be used. The second signal, indicative of afault or of the integrity of the system of FIG. 5 , may be calculatedas:

signal2=A·(dBx/dx)² +B(dBy/dx)²  [5b]

where A and B are constants. The values of A and B may be dependent onthe mounting position (Rs and/or g). The value of A and B are preferablychosen such that the second signal is substantially constant for allangular positions. In preferred embodiment, the ratio of A/B issubstantially equal to K². In a particular embodiment, the value of B ischosen equal to 1, and the value of A is chosen equal to K².

FIG. 6 shows an angular position sensor system 600 according to anotherembodiment of the present invention, which can be seen as a variant ofthe position sensor system 500 of FIG. 5 .

The angular position sensor system 600 of FIG. 6 comprises a two-polemagnet 602 (e.g. a diametrically magnetized two-pole ring magnet or diskmagnet) rotatable around a rotation axis, and a sensor device 601located near a so called “corner position” (e.g. near the periphery ofthe outer circle of the bottom or top surface of the ring or diskmagnet). The ring of disk magnet has an outer radius Ro.

The sensor device 601 preferably comprises a semiconductor substrate andis preferably oriented such that the substrate is substantiallyorthogonal to the rotation axis. In the embodiments shown in FIG. 6 ,the substrate of the sensor device is located in a plane at a predefineddistance “g” (e.g. from 0.5 to 5.0 mm, e.g. equal to about 2.0 mm) froma bottom or top surface of the ring or disk magnet, and the substrate issubstantially perpendicular to the rotation axis. The magnetic center ofthe sensor device 601 is located at a distance “Rs” from the rotationaxis, which may be a value in the range from about 80% to 120% of Ro, orin the range from about 90% to 110% of Ro.

The sensor device 601 of FIG. 6 is configured for measuring acircumferential field component (Bx1, Bx2) and an axial field component(Bz1, Bz2) at two different locations X1, X2 along the X-axis. If anorthogonal coordinate system XYZ is connected to the sensor device, suchthat the X-axis is tangential to a circumferential direction, the Z-axisis perpendicular to the substrate and parallel to the rotation axis, andthe Y-axis is parallel to the substrate and orthogonally intersectingthe rotation axis, then the first signal, indicative of the angularposition of the magnet relative to the sensor device (or vice versa) maybe calculated as follows:

signal1=arctan[K*(dBx/dx)/(dBz/dx)]  [6a]

where K is a constant value, which may be chosen such that the magnitudeof K*(dBx/dx) is substantially equal to magnitude of (dBz/dx).

FIG. 6(e) and FIG. 6(f) show various sensor structures which may be usedto calculate these gradients. The sensor device of FIG. 6(e) uses a socalled “dual disk” structure comprising horizontal Hall elements andIMC. As mentioned above, more information about this structure can befound in US2018372475. The sensor device of FIG. 6(f) comprises twohorizontal Hall elements and two vertical Hall elements, spaced apart bydistance “dx” along the X-axis. Using the latter sensor structure, thevalue of dBx/dx can be calculated as (Vh2-Vh4), and the value of dBz/dxcan be calculated as (Vh1-Vh3). But other sensor structures may also beused. The second signal, indicative of a fault or of the integrity (e.g.(electrical and/or mechanical integrity) of the position sensor systemof FIG. 6 , may be calculated as:

signal2=A·(dBx/dx)² +B(dBz/dx)²  [6b]

where A and B are constants. The values of A and B may be dependent onRs and/or g. The value of A and B are preferably chosen such that thesecond signal is substantially constant for all angular positions. Inpreferred embodiment, the ratio of A/B is substantially equal to K². Ina particular embodiment, the value of B is chosen equal to 1, and thevalue of A is chosen equal to K². The value(s) of A, B, K may bepredefined, e.g. determined during design and e.g. hardcoded, or may bedetermined during a calibration test, and stored in a non-volatilememory of the sensor device.

FIG. 7 shows an angular position sensor system 700 according to anotherembodiment of the present invention, which can be seen as a variant ofthe sensor system 600 of FIG. 6 .

The angular position sensor system 700 of FIG. 7 comprises a two-polemagnet 702 (e.g. a diametrically magnetized two-pole ring magnet or diskmagnet) rotatable around a rotation axis, and a sensor device 701located near a so called “corner position” (e.g. near the periphery ofthe outer circle of the bottom or top surface of the ring or diskmagnet). The ring of disk magnet has an outer radius Ro.

The sensor device 801 preferably comprises a semiconductor substrate andis preferably oriented such that the substrate is substantially parallelto the rotation axis. In the embodiments shown in FIG. 7 , the substrateof the sensor device is substantially located at a predefined distance“g” (e.g. from 0.5 to 5.0 mm, e.g. equal to about 2.0 mm) from a bottomor top surface of the ring or disk magnet. The magnetic center of thesensor device 701 is located at a distance “Rs” from the rotation axis,which may be a value in the range from about 80% to 120% of Ro, or inthe range from about 90% to 110% of Ro.

The sensor device 701 of FIG. 7 is configured for measuring acircumferential field component (Bx1, Bx2) and an axial field component(Bz1, Bz2) at two different locations X1, X2 along the X-axis. If anorthogonal coordinate system XYZ is connected to the sensor device 701,such that the X-axis is tangential to a circumferential direction, theY-axis is parallel to the substrate and parallel to the rotation axis,and the Z-axis is perpendicular to the substrate and orthogonallyintersecting the rotation axis then the first signal, indicative of theangular position of the magnet relative to the sensor device (or viceversa) may be calculated as follows:

signal1=arctan[K*(dBx/dx)/(dBy/dx)]  [7a]

where K is a constant value, which may be chosen such that the magnitudeof K*(dBx/dx) is substantially equal to magnitude of (dBy/dx).

FIG. 7(d) and FIG. 7(e) show various sensor structures which may be usedto calculate these gradients. The sensor device of FIG. 7(d) uses a socalled “dual disk” structure comprising horizontal Hall elements andIMC. This may the same dual disk structure as that of FIG. 6(e), but thesignals may be combined differently. As mentioned above, moreinformation about this structure can be found in US2018372475. Thesensor device of FIG. 7(e) comprises four vertical Hall elements H1 toH4, two (H2, H4) with their axis of maximum sensitivity oriented in theX-direction, and two (H1, H3) with their axis of maximum sensitivityoriented in the Y-direction, spaced apart by distance “dx” along theX-axis. Using the latter sensor structure, the value of dBx/dx can becalculated as (Vh2−Vh4), and the value of dBy/dx can be calculated as(Vh1−Vh3). But other sensor structures may also be used. The secondsignal, indicative of a fault or of the integrity of the system of FIG.7 , may be calculated as:

signal2=A·(dBx/dx)² +B(dBy/dx)²  [7b]

where A and B are constants. The values of A and B may be dependent onthe mounting position (e.g. on Rs and/or g). The value of A and B arepreferably chosen such that the second signal is substantially constantfor all angular positions. In preferred embodiment, the ratio of A/B issubstantially equal to K². In a particular embodiment, the value of B ischosen equal to 1, and the value of A is chosen equal to K². Thevalue(s) of A, B, K may be predefined, e.g. determined during design ande.g. hardcoded, or may be determined during a calibration test, andstored in a non-volatile memory of the sensor device.

It is pointed out that the arrangement of FIG. 7 also works with afour-pole ring or disk magnet, or with a magnet with more than fourpoles.

FIG. 8 shows an angular position sensor system 800 according to anotherembodiment of the present invention. The angular position sensor system800 comprises a four-pole magnet 802 (e.g. an axially magnetized ringmagnet, or an axially magnetized disk magnet) rotatable around arotation axis, and a sensor device 801 located in a so called “off-axis”position (e.g. at a distance of about 0.5 to 5.0 mm above the topsurface or below the bottom surface of the magnet), at a distance Rsfrom the rotation axis. If the magnet is a ring magnet having an innerradius Ri and an outer radius Ro, Rs is preferably a value between Riand Ro, for example substantially halfway between Ri and Ro.

The sensor device 801 is configured for measuring two circumferential(Bx) and two axial (By) magnetic field components with respect to themagnet. The sensor device 801 has a substrate oriented substantiallyperpendicular to the rotation axis, in the example of FIG. 8 , locatedat a distance “g” from the bottom surface of the magnet 802.

If an orthogonal coordinate system X,Y,Z is attached to the sensordevice such that the axes X,Y are parallel to the substrate, and theZ-axis is perpendicular to the substrate, and the X-axis is tangentialto an imaginary circle with radius “Rs”, and the Z-axis is parallel tothe rotation axis, and the Y-axis is oriented radially, then the firstsignal, indicative of the angular position may be written as:

signal1=arctan[K*(dBx/dx)/(dBz/dx)]  [8a]

where K is a constant value, which may be chosen such that the magnitudeof K times the gradient (dBx/dx) is substantially equal to magnitude ofthe gradient (dBz/dx).

And the second signal, indicative of a fault or of the integrity of theposition sensor system 800 may be calculated as:

signal2=A·(dBx/dx)² +B(dBz/dx)²  [8b]

where A and B are constants. The values of A and B may be dependent onthe mounting position (e.g. on Rs and/or g). The value of A and B arepreferably chosen such that the second signal is substantially constantfor all angular positions. In preferred embodiment, the ratio of A/B issubstantially equal to K². In a particular embodiment, the value of B ischosen equal to 1, and the value of A is chosen equal to K². Thevalue(s) of A, B, K may be predefined, e.g. determined during design ande.g. hardcoded, or may be determined during a calibration test, andstored in a non-volatile memory of the sensor device.

FIG. 8(c) and FIG. 8(d) show a few examples of sensor structures whichmay be used to measure said magnetic field components and to determinesaid gradients, but the present invention is not limited thereto, andother suitable sensor structures may also be used. FIG. 8 c shows a“dual disk structure” with four horizontal Hall elements and two IMCdisks. As mentioned above, the disks may have a diameter of about 200micron, and may be spaced apart by about 2.0 mm. FIG. 8(d) shows asensor structure with two horizontal Hall elements and two vertical Hallelements, spaced apart by a predefined distance “dx”, e.g. in the rangefrom about 1.0 mm to about 3.0 mm, but other suitable distances may alsobe used.

In a variant, the magnet 802 may comprise more than four poles, e.g. sixpoles or eight poles, or more than eight poles.

FIG. 9 shows an angular position sensor system 900 according to anotherembodiment of the present invention. The position sensor system 900comprises a multi-pole magnet 902 (e.g. a radially magnetized ringmagnet having at least four, or at least six, or at least eight pole, ormore than eight pole pairs) rotatable around a rotation axis, and asensor device 901.

The sensor device 901 is located at a distance “Rs” from the rotationaxis, Rs being larger than the outer radius Ro of the magnet. The sensordevice 901 is configured for measuring a circumferential magnetic fieldcomponent Bx (tangential to an imaginary circle with radius Rs) and aradial magnetic field component By (with respect to the magnet) at twolocations X1, X2 spaced apart along the X-axis, and has a substrateoriented substantially perpendicular to the rotation axis, and locatedin a plane β perpendicular to the rotation axis, and substantiallymidway between the top and bottom plane of the magnet. If the magnet hasa thickness T, then the substrate is preferably located at a distanceT/2 from the bottom plane and top plane.

If an orthogonal coordinate system X,Y,Z is attached to the sensordevice such that the axes X,Y are parallel to the substrate, and theZ-axis is perpendicular to the substrate, and the X-axis is tangentialto an imaginary circle with radius “Rs”, and the Z-axis is parallel tothe rotation axis, and the Y-axis is oriented radially, then the firstsignal, indicative of the angular position may be written as:

signal1=arctan[K*(dBx/dx)/(dBy/dx)]  [9a]

where K is a constant value, which may be chosen such that the magnitudeof K times the gradient (dBx/dx) is substantially equal to magnitude ofthe gradient (dBy/dx).

And the second signal, indicative of a fault or of the integrity (e.g.electrical an/or mechanical integrity) of the position sensor system maybe calculated as:

signal2=A·(dBx/dx)² +B(dBy/dx)²  [9b]

where A and B are constants. The values of A and B may be dependent onRs and/or h. The value of A and B are preferably chosen such that thesecond signal is substantially constant for all angular positions. Inpreferred embodiment, the ratio of A/B is substantially equal to K². Ina particular embodiment, the value of B is chosen equal to 1, and thevalue of A is chosen equal to K². The value(s) of A, B, K may bepredefined, e.g. determined during design and e.g. hardcoded, or may bedetermined during a calibration test, and stored in a non-volatilememory of the sensor device.

FIG. 9(c) and FIG. 9(d) show a few examples of sensor structures whichmay be used to measure said magnetic field components and to determinesaid gradients, but the present invention is not limited thereto, andother suitable sensor structures may also be used. FIG. 9(c) shows a socalled “dual disk structure” with eight horizontal Hall elements and twoIMC disks. FIG. 9(d) shows a sensor structure with four vertical Hallelements. But other suitable sensor structures may also be used.

In a variant, the magnet 902 may comprise less than eight pole pairs,e.g. four pole pairs or six pole pairs, or more than eight pole pairs,e.g. ten of twelve pole pairs.

FIG. 10 shows an angular position sensor system 1000 according toanother embodiment of the present invention, which can be seen as avariant of FIG. 9 , the main differences being:

that the substrate of the sensor device 1001 is parallel to the rotationaxis of the magnet,the Z-axis (perpendicular to the substrate) is oriented radially withrespect to the magnet, the Y-axis is parallel to the rotation axis,the sensor structure of the sensor device 1001 is configured formeasuring a gradient of the circumferential field component (tangentialto an imaginary circle with radius Rs) and a gradient of the radialfield component with respect to the rotation axis, but these gradientsare calculated differently by the sensor device.

FIG. 10(a) shows a front view, FIG. 10(b) shows a top view. FIG. 10(c)shows a side view.

FIG. 10(d) shows that the sensor device may comprise a “dual disk”structure.

FIG. 10(e) shows that the sensor device may comprise two vertical Hallelements and two horizontal Hall elements, spaced apart in theX-direction, tangential to an imaginary circle with radius “Rs”. Theradius Rs is larger than the outer radius Ro.

If an orthogonal coordinate system X,Y,Z is attached to the sensordevice such that the axes X,Y are parallel to the substrate, and theZ-axis is perpendicular to the substrate, and the X-axis is tangentialto an imaginary circle with radius “Rs”, and the Y-axis is parallel tothe rotation axis, and the Z-axis is perpendicular to the rotation axis,then the first signal, indicative of the angular position may be writtenas:

signal1=arctan[K*(dBx/dx)/(dBz/dx)]  [10a]

where K is a constant value, which may be chosen such that the magnitudeof K times the gradient (dBx/dx) is substantially equal to magnitude ofthe gradient (dBz/dx).

And the second signal, indicative of a fault or of the integrity (e.g.electrical and/or mechanical integrity) of the position sensor systemmay be calculated as:

signal2=A·(dBx/dx)² +B(dBz/dx)²  [10b]

where A and B are constants. The values of A and B may be dependent onRs and/or h. The value of A and B are preferably chosen such that thesecond signal is substantially constant for all angular positions. Inpreferred embodiment, the ratio of A/B is substantially equal to K². Ina particular embodiment, the value of B is chosen equal to 1, and thevalue of A is chosen equal to K². The value(s) of A, B, K may bepredefined, e.g. determined during design and e.g. hardcoded, or may bedetermined during a calibration test, and stored in a non-volatilememory of the sensor device.

FIG. 10(d) and FIG. 10(e) show a few examples of sensor structures whichmay be used to measure said magnetic field components and to determinesaid gradients, but the present invention is not limited thereto, andother suitable sensor structures may also be used. FIG. 10(d) shows a socalled “dual disk structure” with eight horizontal Hall elements and twoIMC disks. FIG. 10(e) shows a sensor structure with two vertical Hallelements and two horizontal Hall elements. But other suitable sensorstructures may also be used. The reader can find more details about the“dual disk structure” and how this can be used to determine magneticfield gradients, in US2018372475A1, which is incorporated herein byreference in its entirety.

FIG. 11 shows a linear position sensor system 1100 according to anotherembodiment of the present invention. The position sensor system 1100comprises a multi-pole magnetic structure 1102 having an elongated shapeextending in a first direction X and having a plurality of magneticpoles magnetised in a second direction Z substantially perpendicular tothe first direction X, and a sensor device 1101 configured for measuringtwo magnetic field components Bx oriented in the first direction X andconfigured for measuring two magnetic field components Bz oriented inthe second direction Z, at two different locations X1, X2 spaced apartin the first direction X, and for calculating a first and secondgradient dBx/dx and dBz/dx based on these field components.

If an orthogonal coordinate system X,Y,Z is connected to the sensordevice, as shown in FIG. 11 , the first signal, indicative of an angularposition, may be calculated in accordance with the following formula:

signal1=arctan[K*(dBx/dx)/(dBz/dx)]  [11a]

where K is a constant value, which may be chosen such that the magnitudeof K times the gradient (dBx/dx) is substantially equal to the magnitudeof the gradient (dBz/dx). This angular position can be converted into alinear position in known manners (e.g. by multiplying the angularposition with a constant, e.g. corresponding to 2*p/360°, and by takinginto account the number of poles from a start position, or in any otherway),and the second signal, indicative of a fault or of the integrity (e.g.electrical and/or mechanical integrity) of the linear position sensorsystem 1100 may be calculated in accordance with the following formula:

signal2=A·(dBx/dx)² +B·(dBz/dx)²  [11b]

FIG. 11(b) and FIG. 11(c) show several sensor structures which can beused to determine said gradients. The sensor structure of FIG. 11(b)comprises a so called “dual disk structure” with four Horizontal Hallplates and two IMC disks (in which, simply stated, the Bx component canbe determined by subtracting the signals obtained from two correspondingHall elements located at opposite sides of the same disk, and the Bzcomponent can be determined by adding the signals obtained from thesetwo Hall elements). The sensor structure of FIG. 11(c) comprises twohorizontal Hall plates H1, H3 configured for measuring Bz at X1 and X2spaced apart along the X-axis, and two vertical Hall plates H2, H4configured for measuring Bx at X1 and X2.

In preferred embodiments, dx is smaller than p/4 or smaller than p/6, orsmaller than p/8 or smaller than p/10, or smaller than p/12, p being thedistance between centers of adjacent poles. But the invention is notlimited hereto, and other values of dx relative to p may also be used.

FIG. 12 illustrates a flowchart of a method 1200 of determining a firstsignal (or first value) indicative of a position, and a second signal(or second value) indicative of a fault or of the integrity (e.g.electrical and/or mechanical integrity) of a position sensor system, thesystem comprising a magnetic source and a sensor device movably mountedrelative to the magnetic source, or vice versa, wherein both the firstand the second signal are insensitive to an external disturbance field.The method 1200 comprises the steps of:

-   -   a) measuring 1201 at least three magnetic field values (e.g.        Vh0, Vhc, Vh1 in FIG. 4(c); or Vh1 to Vh4 in FIG. 5 to FIG. 10 )        of the magnetic field generated by the magnetic source;    -   b) determining 1202 at least two magnetic field gradients (e.g.        dBu/du and dBx/dx in FIGS. 1, 2 ; or dBz/dx and dBz/dy in FIG. 4        ; or dBx/dx and dBy/dx in FIGS. 5, 7, 9 ; or dBx/dx and dBz/dx        in FIGS. 6, 8, 10 ) or at least two or at least three magnetic        field differences (see e.g. FIG. 14(a) to FIG. 16(d)) based on        said at least three magnetic field values;    -   c) deriving 1203 from said at least two magnetic field gradients        or from said at least two or at least three magnetic field        differences a first signal or a first value “signal1” indicative        of a (e.g. linear or angular) position of the sensor device;    -   d) deriving 1204 from said at least two magnetic field gradients        or from said at least two or at least three magnetic field        differences a second signal “signal2” indicative of a fault or        of the integrity (e.g. electrical and/or mechanical integrity)        of the position sensor system, e.g. indicative of the presence        or absence of the magnetic source.

Step a) may comprise: measuring three magnetic field values oriented ina single direction at three different locations, or measuring twomagnetic field values at a first location and measuring two magneticfield values at a second location different from the first location).

Step b) may comprise: measuring said spatial gradients along a directionof relative movement, for example in case of an angular position sensorsystem, in a circumferential direction, or in a direction tangential toan imaginary circle having a center located on the rotation axis.

In an embodiment, step b) may comprise: determining differences betweensignals obtained from various horizontal Hall elements located on avirtual circle, as illustrated for example in FIG. 14(c) or FIG. 14(d).

In an embodiment, step b) may comprise: determining differences betweensignals obtained from horizontal Hall elements located on a virtualcircle and a signal obtained from a horizontal Hall element located in acenter of the circle, as illustrated for example in FIG. 15(c) or FIG.15(d).

In an embodiment, step b) may comprise: calculating an average signal ofthe signals obtained from horizontal Hall elements located on a circle,and calculating differences between signals obtained from the horizontalHall elements located on the virtual circle and the average signal, asillustrated or example in FIG. 16(c) or FIG. 16(d).

Step c) may further comprise: converting the first signal into anangular position, e.g. in accordance with the formula: signal1=N*θ,where N is an integer number and θ is the mechanical angle. The value ofN is typically equal to 1 for a two-pole magnet, and is typically equalto 2 for a four-pole magnet.

In case of a linear position sensor, step c) may further compriseconverting the angular position value into a linear position value, forexample by taking into account the number of the pole under which thesensor device is located.

The method may optionally further comprise step e) of:

-   -   e) comparing 1205 the second signal with at least one threshold        value, and outputting a result of the comparison, for example in        the form of a low or high voltage level, corresponding to a        “good” or bad system integrity. It is also possible to compare        the second signal with more than one threshold value, e.g. with        a lower threshold value and with an upper threshold value, and        to output a result of the comparison in the form of a        “good-signal”, a “warning-signal”, or an “error-signal”. The        skilled person having the benefit of the present disclosure can        easily think of other variants.

FIG. 13 is a schematic block diagram of an exemplary position sensordevice 1302 as can be used in embodiments of the present invention.Position sensor devices are known in the art, but a brief description isprovided for completeness.

The position sensor device 1302 of FIG. 13 comprises a plurality ofmagnetic sensitive elements (e.g. in the example of FIG. 1 eighthorizontal Hall elements H0 to H7; in the example of FIG. 2 fourvertical Hall elements; etc.), arranged in a particular manner on asemiconductor substrate as described above (e.g. in FIG. 1 to FIG. 11 )

The position sensor device 1302 further comprises a processor or aprocessing circuit, for example a programmable processing unit 1320adapted for determining a first and a second gradient signal based onthe signals obtained from the magnetic sensor elements, e.g. bysummation or subtraction of two or more values.

The processing unit 1320 is preferably further adapted for determining aposition, e.g. an angular position based on a ratio of these gradientsignals, for example using a look-up table and interpolation, or bymaking use of goniometric functions (e.g. an arctangent function) or inany other suitable way. In case of a linear position sensor system, theprocessing unit 1320 may be further adapted for converting this angularposition value into a linear position value.

The position value may be output by the controller as a first outputsignal “POS”.

According to an underlying principle of the present invention, thecontroller also calculates and optionally also outputs a second signal“signal2”, indicative of a fault or of the integrity of the system, or avalue derived therefrom, for example after comparing the second signalwith one or more predefined threshold values.

In an embodiment, the controller 1320 is configured for testing whetherthe second signal lies in a first predefined range, and if the outcomeof this test is TRUE, the controller outputs an integrity signal “INT”having a first level (e.g. logical ‘1’) corresponding to a “good”situation, and if the outcome of the test is FALSE, the controlleroutputs an integrity signal having a second level (e.g. a logical ‘0’)corresponding to a “bad” situation, or vice versa. The output signalsmay be provided as digital signals, or as analog signals, orcombinations hereof.

While not explicitly shown, the sensor device 1320 typically furthercomprises biasing circuitry, readout circuitry, one or more amplifiers,analog-to-digital convertors (ADC), etc. Such circuits are well known inthe art, but are not the main focus of the present invention.

While the present invention is mainly described with horizontal Hallelements and/or vertical Hall elements, the present invention is notlimited to this type of magnetic sensitive elements, and other types ofmagnetic sensor elements may also be used, for example circular Hallelements, or magneto-resistive elements, e.g. XMR or GMR elements.

FIG. 14 (a) and FIG. 14(b) show another embodiment of a sensor system1400 comprising a two-pole magnet 1402 and a sensor device 1401comprising three horizontal Hall elements H1, H2, H3 located on avirtual circle and angularly spaced apart by multiples of 120°. Themagnet 1402 may be an axially or a diametrically magnetized ring or diskmagnet. The center of the virtual circle is preferably located on therotation axis of the magnet. Each of the horizontal Hall elements H1,H2, H3 measures a magnetic field component Bz oriented in theZ-direction, perpendicular to the semiconductor substrate. The valuesprovided by the Hall elements H1, H2, H3 are Vh1, Vh2, and Vh3respectively.

FIG. 14(a) is a schematic representation of the sensor device 1401.

FIG. 14(b) is a perspective view of the sensor system 1400.

FIG. 14(c) shows simulation results of a sum of squares of differencesbetween pairs of two magnetic field components, e.g. in accordance withthe formula:

Signal2=(Vh1−Vh2)²+(Vh2−Vh3)²+(Vh3−Vh1)²

where signal2 is the signal indicative of a fault, Vh1, Vh2 and Vh3 aresignals provided by the horizontal Hall elements (or derived therefrom,e.g. after amplification, digitization, etc.). Since the horizontal Hallelements H1, H2, H3 are oriented in the same (Z) direction, each of thedifference signals (Vh1−Vh2), (Vh2−Vh3), and (Vh3−Vh1) is substantiallyinsensitive to an external disturbance field, and hence also the sum ofthe squares of these difference signals is highly insensitive to anexternal disturbance field.

In the example shown, the sum of squares is constant over the full 360°measurement range. In practice, there may be a small variation on thesignal (e.g. due to differences in magnetic sensitivity of the sensorelements). By calculating the sum and by comparing the sum with a firstthreshold smaller than said constant, and/or by comparing the sum with asecond threshold larger than said constant, and by testing whether thesum is a value smaller than the lower threshold, and/or larger than theupper threshold, and/or a value between these two thresholds, it ispossible to detect certain faults. In a practical implementation, anaverage value or median value may be determined during design and may behardcoded, or an average value or median value may be determined duringa calibration test and stored in a non-volatile memory of the sensordevice, which may be retrieved during actual use.

The first threshold may be a value in the range from 75% to 99% of theabove-mentioned average value, e.g. equal to about 75%, or equal toabout 80%, or equal to about 85%, or equal to about 90%, or equal toabout 95%, or equal to about 96%, or equal to about 97%, or equal toabout 98%. The second threshold may be a value in the range from 101% to125% of the above-mentioned average value, e.g. equal to about 102%, orequal to about 103%, or equal to about 104%, or equal to about 105%, orequal to about 110%, or equal to about 115%, or equal to about 120%, orequal to about 125%.

As a numerical example, if the individual signals would have anamplitude of 1.0, the difference signals would have an amplitude ofabout 1.73, and the average value would be equal to about 4.5. If thefirst threshold would be set at 85% of 4.5 (approximately 3.83), and thesecond threshold would be set at 115% of 4.5 (approximately 5.18), thesecond signal will indicate that the “system integrity is OK” if thecalculated signal is a value in the range from 3.83 to 5.18 and willindicate that “a fault has occurred” if the calculated sum is a valueoutside this range.

FIG. 14(d) shows simulation results of another second signal Signal2′indicative of a fault, which is a variant of the formula of FIG. 14(c),wherein the second signal Signal2′ is calculated as a sum of absolutevalues of differences between pairs of two magnetic field components,e.g. in accordance with the formula:

Signal2′=abs(Vh1−Vh2)²+abs(Vh2−Vh3)²+abs(Vh3−Vh1)²

where signal2 is the signal indicative of a fault, Vh1, Vh2 and Vh3 aresignals provided by the horizontal Hall elements H1 to H3 (or derivedtherefrom, e.g. after amplification, digitization, etc.). Since thehorizontal Hall elements are oriented in the same (Z) direction, each ofthe difference signals (Vh1-Vh2), (Vh2-Vh3), and (Vh3-Vh1) issubstantially insensitive to an external disturbance field, and hencealso the sum of the absolute values of these differences is highlyinsensitive to an external disturbance field.

As a numerical example, if the original signals Vh1, Vh2, Vh3 have anamplitude of 1.0, the difference signals will have an amplitude of about1.73, and the sum of the absolute values of these differences will bevalues in the range from about 3.00 to about 3.46. Thus, the averagevalue is equal to about 3.23, and “valid” sums of absolute values ofdifferences are values in the range from about 3.00 to about 3.46, whichis about 3.23+/− about 7%.

It came as a big surprise that the sum of absolute values of thedifferences has such as small “ripple” (only about +/−7%), especially inview of the simple arithmetic: taking an absolute value is a very simpleoperation (only requires omitting the sign), in contrast to for examplecalculating a square or a polynomial, which typically requires ahardware multiplier, and typically requires more processing time.

In practice, taking into account typical tolerances (e.g. mechanicalmounting tolerances), a slightly larger tolerance margin may be chosen,for example ±10%, or ±12%, or ±14%, or ±16%, or ±18%, or ±20%. Ofcourse, the larger this tolerance range, the less sensitive the faultdetection.

FIG. 15 (a) and FIG. 15(b) show another embodiment of a sensor system1500 comprising a two-pole magnet and a sensor device 1501 comprisingthree horizontal Hall elements H1, H2, H3 located on a circle andangularly spaced apart by multiples of 120°, and a fourth horizontalHall element Hc located in the center of the circle. The magnet may bean axially or a diametrically magnetized ring or disk magnet. The centerof the virtual circle is preferably located on the rotation axis of themagnet. Each of the horizontal Hall elements H1, H2, H3, Hc measures amagnetic field component Bz oriented in the Z-direction, perpendicularto the semiconductor substrate. The values provided by the Hall elementsH1, H2, H3, Hc are Vh1, Vh2, Vh3, Vhc respectively.

FIG. 15(a) is a schematic representation of the sensor device 1501.

FIG. 15(b) is a perspective view of the sensor system 1500.

FIG. 15(c) shows simulation results of a sum of squares of differencesbetween each of the Hall elements H1, H2, H3 on the circle and thecentral Hall element Hc, e.g. in accordance with the formula:

Signal2=(Vh1−Vhc)²+(Vh2−Vhc)²+(Vh3−Vhc)²

where Signal2′ is the signal indicative of a fault, Vh1, Vh2, Vh3 andVhc are signals provided by the horizontal Hall elements H1, H2, H3, Hc(or derived therefrom, e.g. after amplification, digitization, etc.).Since the horizontal Hall elements are oriented in the same (Z)direction, each of the difference signals (Vh1−Vhc), (Vh2−Vhc), and(Vh3−Vhc) is substantially insensitive to an external disturbance field,and hence also the sum of the squares of these difference signals ishighly insensitive to an external disturbance field.

In the example shown, the sum is constant over the full 360° measurementrange. In practice, there may be a small variation on the signal (e.g.due to differences of magnetic sensitivity of the sensor elements). Bycalculating the sum and by comparing the sum with a first thresholdsmaller than said constant, and/or by comparing the sum with a secondthreshold larger than said constant, and by testing whether the sum is avalue between these two thresholds, it is possible to detect certainfaults. In a practical implementation, an average value or median valuemay be determined during design and may be hardcoded, or an averagevalue or median value may be determined during a calibration test andstored in a non-volatile memory of the sensor device, which may beretrieved during actual use.

The first threshold may be a value in the range from 75% to 99% of theabove-mentioned average value, e.g. equal to about 75%, or equal toabout 80%, or equal to about 85%, or equal to about 90%, or equal toabout 95%, or equal to about 96%, or equal to about 97%, or equal toabout 98%. The second threshold may be a value in the range from 101% to125% of the above-mentioned average value, e.g. equal to about 102%, orequal to about 103%, or equal to about 104%, or equal to about 105%, orequal to about 110%, or equal to about 115%, or equal to about 120%, orequal to about 125%.

As a numerical example, if the individual signals Vh1, Vh2, Vh3 wouldhave an amplitude of 1.0, the difference signals would also have anamplitude of about 1.0, and the average value would be equal to about1.5. If the first threshold would be set at 85% of 1.5 (approximately1.28), and if the second threshold would be set at 115% of 1.5(approximately 1.73), the second signal will indicate that the no faultis detected (thus the system integrity is good) if the calculated signalis a value in the range from 1.28 to 1.73 and will indicate that “afault is detected” if the calculated sum is a value outside this range.

FIG. 15(d) shows simulation results of another second signal Signal2′indicative of a fault, which is a variant of the formula of FIG. 15(c),wherein the second signal Signal2′ is calculated as a sum of absolutevalues of differences between each of the Hall elements H1, H2, H3 onthe circle and the central element Hc, e.g. in accordance with theformula:

Signal2′=abs(Vh1−Vhc)²+abs(Vh2−Vhc)²+abs(Vh3−Vhc)²

where Signal2′ is the signal indicative of a fault, Vh1, Vh2 and Vh3 aresignals provided by the horizontal Hall elements H1, H2, H3 located onthe circle (or derived therefrom, e.g. after amplification,digitization, etc.), and Vhc is the signal provided by the central Hallelement Hc (or derived therefrom). Since the horizontal Hall elementsare oriented in the same (Z) direction, each of the difference signals(Vh1−Vhc), (Vh2−Vhc), and (Vh3−Vhc) is substantially insensitive to anexternal disturbance field, and hence also the sum of the absolutevalues of these differences is highly insensitive to an externaldisturbance field.

As a numerical example, if the original signals Vh1, Vh2, Vh3 have anamplitude of 1.0, the difference signals will also have an amplitude ofabout 1.0, and the sum of the absolute values of these differences willbe values in the range from about 1.73 to about 2.00. Thus, the averagevalue is equal to about 1.87, and “valid” sums of absolute values ofdifferences are values in the range from about 1.73 to about 2.00, whichis about 1.87+/− about 7%.

It came as a big surprise that the sum of absolute values of thedifferences has such as small “ripple” (only about +/−7%), especially inview of the simple arithmetic: taking an absolute value is a very simpleoperation (only requires omitting the sign), in contrast to for examplecalculating a square or a polynomial, which typically requires ahardware multiplier, and typically requires more processing time.

In practice, taking into account typical tolerances (e.g. mechanicalmounting tolerances), a slightly larger tolerance margin may be chosen,for example ±10%, or ±12%, or ±14%, or ±16%, or ±18%, or ±20%. Ofcourse, the larger this tolerance range, the less sensitive the faultdetection.

FIG. 16(a) and FIG. 16(b) show another embodiment of a sensor system1600 comprising a two-pole magnet and a sensor device 1601 comprisingthree horizontal Hall elements H1, H2, H3 located on a circle andangularly spaced apart by multiples of 120°. The sensor device 1601 isconfigured to determine (e.g. in hardware and/or in software) an averagesignal Vavg in accordance with the following formula:

Vavg=(Vh1+Vh2+Vh3)/3,

where Vh1, Vh2, Vh3 are the signals provided by the horizontal Hallelements H1, H2, H3, and Vavg is the average of these three signals.

FIG. 16(c) shows simulation results of a sum of squares of differencesbetween each magnetic field component and said average signal. Thissimulation provides the same result as shown in FIG. 15(c), and all thatis mentioned above is also applicable here.

FIG. 16(d) shows simulation results of a sum of absolute values ofdifferences between each magnetic field component and said averagesignal. This simulation provides the same result as shown in FIG. 15(d),and all that is mentioned above is also applicable here.

While the embodiments of FIG. 14(a)-(d), FIG. 15(a)-(d) and FIG.16(a)-(d) are shown for a sensor system comprising a two-pole magnet anda sensor device comprising three horizontal Hall elements arranged on acircle, and optionally one central Hall element, the same principlesalso apply to a sensor system (not shown) comprising a four-pole magnet(e.g. a four-pole ring or disk magnet) and a sensor device (not shown)comprising six horizontal Hall elements arranged on a circle, angularlyspaced apart by multiples of 60°, and optionally a central element Hc.The second signal may be calculated as:

Signal2=(Vh1−Vh2)²+(Vh2−Vh3)²+(Vh3−Vh4)²+(Vh4−Vh5)²+(Vh5−Vh6)²+(Vh6−Vh1)²,

where a sum of squares of differences is calculated between signalsobtained from adjacent Hall elements. It can be shown that this sum ofsignals is substantially constant. The second signal may also becalculated as:

Signal2′=abs(Vh1−Vh2)+abs(Vh2−Vh3)+abs(Vh3−Vh4)+abs(Vh4−Vh5)+abs(Vh5−Vh6)+abs(Vh6−Vh1),

where a sum of absolute values of differences is calculated betweensignals obtained from adjacent Hall elements. It can be shown that thissum of signals has a relatively small ripple.

While a second signal in the form of a sum of absolute values isexplicitly described above only for the systems shown in FIG. 4(c), FIG.14(b), FIG. 15(b) and FIG. 16(b), it shall be clear to the skilledreader having the benefit of the present disclosure, that also in theother systems described above, a second signal in the form of a sum ofsquares of gradients or differences can be used, or in the form of a sumof absolute values of gradients or differences can be used, or in theform of another function which is substantially constant over themeasurement range, such as for example a polynomial function of a degreeof at least two, for example a polynomial comprising only second orderand fourth order terms, or a polynomial comprising only even orderterms, but the present invention is not limited hereto.

1. A position sensor device, comprising: at least two magnetic sensorsspaced apart in an X-direction, each of the at least two magneticsensors configured to measure at least two orthogonal magnetic fieldcomponents; and a processing circuit configured for: calculating twopairwise differences, calculating and outputting a first signalindicative of a position of the device relative to a magnetic source,based on a ratio of said two pairwise differences, calculating andoutputting a second signal indicative of a fault, the second signalbased on a sum of squares of the two pairwise differences or a sum ofabsolute values of the two pairwise differences.
 2. The position sensordevice according to claim 1, the position sensor device furthercomprising a substrate, wherein each of the at least two orthogonalmagnetic field components are oriented parallel to the substrate.
 3. Theposition sensor device according to claim 1, the position sensor devicefurther comprising a substrate, wherein a first of the at least twoorthogonal magnetic field components is oriented parallel to thesubstrate and a second of the at least two orthogonal magnetic fieldcomponents is oriented perpendicular to the substrate.
 4. The positionsensor device according to claim 1, wherein the second signal is basedon a comparison of the sum of squares or the sum of absolute values withone or more threshold values.
 5. The position sensor device according toclaim 1, wherein the position comprises an angular position.
 6. Theposition sensor device according to claim 1, wherein the positioncomprises a linear position.
 7. The position sensor device according toclaim 1, wherein each of the at least two magnetic sensors comprises ahorizontal hall element and a vertical hall element; or wherein each ofthe at least two magnetic sensors comprises two vertical Hall elementswith their axes of maximum sensitivity oriented perpendicular to eachother.
 8. The position sensor device according to claim 1, wherein eachof the at least two magnetic sensors comprises an integrated magneticconcentrator IMC and two horizontal hall elements arranged near aperiphery of the integrated magnetic concentrator.
 9. A position sensorsystem, comprising: the position sensor device according to claim 1; andthe magnetic source; wherein the magnetic source comprises a magnethaving only two poles or having at least two poles.
 10. A positionsensor device, comprising: three magnetic sensors located on a virtualcircle and spaced apart by multiples of 120°, each of the three magneticsensors configured to measure a magnetic field component orientedperpendicular to a substrate of the device; and a processing circuitconfigured for: calculating an average of the measured magnetic fieldcomponents, calculating three difference signals, each difference signalcomprising a difference between one of the measured magnetic fieldcomponents and the average, calculating a first signal indicative of anangular position of the device relative to a magnetic source based onthe difference signals, calculating and outputting a second signalindicative of an integrity signal, a fault signal, or a magnet signal,the magnet signal indicative of a presence or absence of a magnet, andwherein the second signal is based on a sum of squares of the differencesignals or a sum of absolute values of the difference signals.
 11. Theposition sensor device according to claim 10, wherein each of the threemagnetic sensors comprises a horizontal hall element.
 12. The positionsensor device according to claim 10, wherein the second signal is basedon a comparison of the sum of squares of the difference signals or thesum of absolute values of the difference signals with one or morethreshold values.
 13. The position sensor device according to claim 10,wherein the substrate comprises a semiconductor substrate.
 14. Aposition sensor system, comprising: the position sensor device accordingto claim 10; and the magnetic source; wherein the magnetic sourcecomprises a magnet having only two poles or having at least two poles.15. A position sensor device, comprising: a substrate comprising atleast four pairs of sensor elements located on a virtual circle, eachpair configured for measuring magnetic field components oriented indifferent directions parallel to the substrate; and a processing circuitconfigured for: determining at least four magnetic field gradients alongat least four different directions parallel to the substrate andangularly spaced by 45°, based on said measured magnetic fieldcomponents, calculating a first signal indicative of a position of theposition sensor device relative to a magnetic source, calculating andoutputting a second signal indicative of an integrity signal, a faultsignal, or a magnet signal, the magnet signal indicative of a presenceor absence of a magnet, the second signal based on the followingformula:signal 2=(dBx/dx−dBy/dy)²+(dBu/du−dBv/dv)² or a value derived therefrom,wherein Bx is a magnetic field component oriented in a first direction Xparallel to the substrate, By is a magnetic field component oriented ina second direction Y parallel to the substrate and perpendicular to thefirst direction X, Bu is a magnetic field component oriented in a thirddirection U parallel to the substrate and forming an angle of 45° withthe first direction X, and By is a magnetic field component oriented ina fourth direction V parallel to the substrate and perpendicular to thethird direction U.
 16. The position sensor device according to claim 15,wherein the sensor elements are provided in a single chip.
 17. Theposition sensor device according to claim 15, wherein the positionsensor device comprises at least one integrated magnetic concentrator;and wherein each of the sensor elements comprises a horizontal hallelement arranged near a periphery of said at least one integratedmagnetic concentrator.
 18. A position sensor system, comprising: theposition sensor device according to claim 15; and the magnetic source;wherein the magnetic source comprises a magnet having only four poles orhaving at least four poles.
 19. The position sensor system according toclaim 18, wherein the magnet is rotatable about a rotation axis and theposition sensor device is located substantially on said rotation axis.20. The position sensor system according to claim 19, wherein thesubstrate comprises a semiconductor substrate oriented substantiallyorthogonal to the rotation axis.